Interesting fact which is depressing

Me and my cousin were born 6 days apart for each other and grew up around each other as my aunt lives 6 doors down from my house. So in theroy we should have developed at similar rates but Because of how differently we were treated i learnt to crawl and walk long before him because he was constantly being held and carried by people. But he learnt to talk 8 months before me for the same reason. Pretty screwed up that blatant favourtisim affects how fast children develop.