Do Identical Twins Milestone at the Same Time? This Explains It All

| Reviewed By Amanda Lundberg, BSN, RN

When you have twin babies, you have the potential for twice the happiness when marking important achievements. However, it can also mean twice the concern if your twins are not reaching these milestones at the anticipated rate.

Many new parents of twins get concerned if their identical twins do not reach milestones at the same time. 

Do identical twins milestone at the same time? Identical twins will often reach milestones at approximately the same time, but this is not always the case. While identical twins’ development may be very similar, it is important to remember that each twin is unique and will progress at their own pace, regardless of how their twin is developing.

If you are concerned about your identical twins’ development or are preparing to raise identical twins, you are in the right place to gain a bit more understanding about twins’ development when it comes to milestones. 

Identical Twins & Milestones – What To Know

Parenting twins is definitely rewarding, but it often feels like there are double the worries everywhere you look.

While worrying is a normal part of being a parent, seeking out information can help set your mind at ease (at least about some things). Let’s take a close look at what you can expect in terms of development and milestones.

How Does Being a Twin Affect Development? 

Many new parents of twins will wonder if their children will experience developmental delays compared to their singleton counterparts.

There are a lot of factors that affect physical and cognitive development in children. Age, size, weight, parental involvement, social interaction, and genetics are just a few. 

While most twins can be expected to hit milestones at roughly the same time as other children, researchers have found that it is not unusual for twins to experience minor delays in their physical and cognitive development compared to other children their age.

Will Identical Twins Develop at the Same Rate? 

One would think that identical twins would be like little robots when it comes to development, hitting every milestone at the exact same time because they are, well, identical!

Believe it or not, this is not always the case. While most identical twins will reach their milestones around the same time, it is normal for there to be some variance. 

Identical twins share every fraction of their DNA, but that does not mean that they will always begin to walk or talk at the same time.

It is important to remember that every child is different. Identical twins are individuals and very different, even though they might have a genetic double at their side. 

Do Twins Take Longer To Hit Milestones?

Research has shown that it is possible for twins to experience minor delays in both their physical and cognitive development.

This is not always the case, and the delays are often so minor and treatable that they are not generally a cause for concern. 

Twins usually have different circumstances beyond their control that may affect their development.

Physically, twins are usually smaller from birth, and therefore, their weight and size may not align with their age.

This may result in them developing gross motor skills, such as crawling and walking, later than other children their age simply because they are smaller.

Language delays are also common among twins. According to the LOOKING at Language study, 38% of twins experienced late language emergence compared to 19% of singletons.

At the age of two, 71% of twins were not combining words while 83% of singletons were able to combine words. 

Speech-language pathologists from Wee talkers attribute speech delays to differences in social environments and social language experiences.

Twins may not have as much language stimulation as a singleton because they share the attention of their parent or caretaker and may not have as much one-on-one, quality interactions and attention as other singleton children.

This is one theory for why twins may develop cognitive abilities, such as language, a bit later than singletons. Fortunately, however, most delays are corrected by the age of four. 

Why Identical Twins May Develop at Different Rates

An important thing to remember when it comes to milestones is that physical readiness is only one part of the equation. Personality, temperament, and intellectual ability are also key factors.

Identical twins may look alike physically, but they can be completely different when it comes to personality and how they act.

One twin may be adventurous and be motivated to get across the room a little faster while the other may be content sitting and watching for a while.

Additionally, if one twin has special needs, their milestone timeline certainly will look a little different than that of their identical twin. 

How To Adjust Milestone Ages for Twins

Determining the adjusted age for twins is fairly simple. Full term for pregnancy is 40 weeks. Most twins are born before week 40.

To calculate adjusted age, simply subtract how early your twins were from their actual age. For example, if your twins were born at 35 weeks, at 6 months old their adjusted age would be just under 5 months old.

Therefore, whatever milestones are “expected” at 6 months, your twins would likely reach closer to 7 or 8 months of age. 

How To Track Identical Twins’ Milestones

When you have twins, it is easy to want to compare everything they do to each other and, honestly, every other baby you know!

Keep in mind that they will be different from each other, including their developmental timeline. Here are some tips for tracking your twins’ milestones: 

1. Pay Attention to Age Range Rather Than Exact Weeks or Months

You will notice that most milestones have a range, such as 4-6 months. One of your twins may hit a milestone at the beginning of the range and the other toward the end. That is totally fine!

2. Remember To Adjust for Prematurity

Twins are often a little behind from being born early. When considering milestone age ranges, remember to give them a little bit of a grace period depending on how early they made their arrival. 

3. Track Your Twins’ Progression Individually

One of the first things my twins’ pediatrician told me was to not compare them to each other.

My son appeared to be gaining weight faster than my daughter, and it concerned me. What I didn’t realize was that she had actually gained MORE weight than he did considering how small she was when she was born.

Each twin is their own person and on their own timeline. The important thing is that they are hitting milestones, regardless of when their twin hits them. 

Things To Keep in Mind About Identical Twins and Milestones

  • Twins might hit milestones a tad behind normal milestone age ranges. They should not be too far behind, however. 
  • Identical twins might not reach all milestones at the same time. 
  • Double babies means double the work. Remember to focus on each baby individually at times to help their individual development. 
  • Do not compare your twins’ development to each other. Look at each one individually when measuring their progression. 
Two cute twin brothers on their tummies against a white background.

How Important Are Baby Milestones? 

Baby milestones are a good thing! They help us make sure our babies are healthy and on track. They also offer clues about a baby’s developmental health.

Reaching milestones at the typical age shows a child is progressing as expected while reaching them later can indicate a developmental delay and can cue intervention if necessary.

Not reaching certain milestones by a certain age can be a red flag that extra support and services may be needed to help the child reach their full potential. 

What Baby Milestones Are the Most Important? 

These are some of the most important milestones for your baby’s first year: 

2 Months

  • Makes sounds other than crying
  • Making eye contact and watching you as you move
  • Holds head up when on tummy
  • Moves both arms and legs

4 Months

  • Smiling and chuckles
  • Cooing
  • Turns head to sound of your voice
  • Looks at hands with interest and brings hands to mouth
  • Holds head steady without support
  • Holds a toy when you put it in his hand

6 Months

  • Knows familiar people
  • Laughs
  • Blows “raspberries” and squeals
  • Makes sounds back at you
  • Reaches to grab toys
  • Rolls from tummy to back

9 Months

  • Shy around strangers
  • Several facial expressions
  • Recognizes name
  • Makes different sounds like “mama” and “baba”
  • Lifts arms to be picked up
  • Moves things from one hand to the other and rakes food toward himself
  • Sits without support

12 Months

  • Plays games like “pat a cake”
  • Waves bye bye
  • Calls parents “mama” or “dada”
  • Understands “no”
  • Fine motor skills to put things in a cup
  • Object permanence
  • Pulls up to stand and cruises along furniture

Signs of Developmental Delay

There are many different signs of delay, and they will vary depending on the specific situation. Some of the most common for infants and young toddlers include: 

  • Learning and developing much more slowly than other children the same age
  • Gross motor skills (rolling, crawling, walking) much later than appropriate
  • Difficulty communicating or socializing
  • Difficulties talking or talking late
  • Difficulty with problem-solving or logical thinking

When To Worry About Your Twins’ Development

Deakin University’s Associate Professor Jeff Craig, an internationally recognized expert on twins and the president of the International Society for Twin Studies, advises parents of twins about how to approach milestones and their children:

“When it comes to milestones like crawling and walking, even with singletons, the developmental pediatricians say there’s a wide range of when these milestones can happen. But it’s difficult to say exactly what governs that.”

“The general advice a pediatrician will usually give in regards to milestones is to expect a large window of opportunity. But if you ever suspect one [or both] of the twins is taking too long to reach a milestone, make sure you see a developmental pediatrician. That way you’ll get a real understanding.”

Pediatricians will always take the fact that your children are twins into consideration when assessing their development; however, twins should not always be too far behind.

If your twin is several months behind the “average” age range for milestones, consult with a developmental pediatrician. 

Related Questions: 

Are Twins More Likely To Have Disabilities? 

Some studies show that twins are more likely to have disabilities compared to singletons due to a prevalence of low birth weight and premature births. 

When Do Twins Start Walking?

Similar to singleton babies, most twins will start walking between 10 and 15 months of age. 


Double the babies means double the excitement when hitting milestones! Hopefully, you have a better understanding of your twins’ development and can celebrate each individual milestone as they come!