How Birth Order Is Determined - the scientific reason

Collin -  mommy, do you know why I was born first before Grace?

Me - because that was God's plan for our family.

C - No, it's because when all the babies were in your tummy we were having races and contests, and I was the winner so I was born first.  Then Grace was next.

(Can you tell he's my super-competitive one?  Everything is a contest & somehow he makes the rules so that he always wins.  We are working on a humble spirit & putting others first.)