Your older child spoke in full sentences by two, rode a bicycle early, and sailed through school readiness without much fuss. Your younger one is approaching the same ages now, and almost nothing is following the same timeline. You keep comparing notes in your head, and the gap between the two feels larger than you expected it to.
Why Siblings Rarely Develop on the Same Timeline
Each child's development is shaped by their own individual pace across different skill areas, such as language, movement and social confidence, and two children growing up in the same household can still show genuinely different patterns and timing in each of these areas. A younger sibling may also experience childhood differently, with less one-on-one attention at certain ages or more exposure to an older sibling's pace, both of which can shift how skills show up without necessarily reflecting a problem.
Signs the Difference Is Worth a Closer Look
- The gap is not in one area alone but shows up across several different areas of development at once.
- Skills are not just slower to arrive but seem to be missing certain expected steps along the way.
- The difference compared to the older sibling is large enough that a teacher or doctor has also mentioned it independently.
- Your own instinct, beyond the sibling comparison, says something feels different about how your younger child is progressing.
What You Can Try at Home
- Track your younger child's own progress over time rather than measuring every milestone against the older sibling.
- Note specific examples of skills and timing, rather than a general feeling of being behind, to discuss with a professional if needed.
- Give your younger child dedicated one-on-one time for practising specific skills, separate from sibling-led play.
- Talk to your paediatrician about the specific milestones you are noticing, rather than the sibling comparison itself.
What Tends to Make It Worse
Constantly comparing the two children out loud, even with good intentions, can add pressure on the younger child and sometimes delay parents from looking closely at the younger child's own individual pattern. Dismissing a genuine, persistent gap as simply personality or birth order without checking further can also mean a real underlying difference goes unaddressed for longer than necessary. Well-meaning relatives insisting that the older sibling was also a late bloomer can sometimes discourage parents from following up on a pattern that actually looks different this time.
When It Is Worth an Occupational Therapy Assessment
Some difference between siblings is completely normal, and many younger children catch up in their own time. It is worth an assessment if the gap spans multiple areas of development, includes skills that seem genuinely missing rather than simply delayed, or has already been flagged by a teacher or doctor. Trusting your own observations as a parent, alongside this kind of feedback, is generally a reliable guide for deciding whether to look further. An occupational therapist can assess your child's development on its own terms, separate from sibling comparison. Our developmental delay page explains how this kind of support is usually approached.
Frequently Asked Questions
Is it unusual for siblings to develop very differently?
No, it is actually quite common. Birth order, individual temperament and even how much one-on-one attention each child gets at a given age can all lead to genuinely different development timelines between siblings in the same family.
Should I stop comparing my children's milestones altogether?
It is reasonable to stop comparing out loud, since this can add pressure, while still privately noting any specific milestones that concern you so you have concrete examples to discuss with a professional if needed.
How do I know if this is just personality or something more?
A general difference in pace or temperament usually shows up unevenly, stronger in some areas and typical in others. A pattern that spans many areas at once, or includes skills that seem to be missing rather than simply slower, is worth checking more closely.
Will my younger child likely catch up on their own?
Many children do catch up in their own time, especially with small gaps in one or two areas. Persistent or wide gaps across several areas of development are less likely to close on their own without some support.
