Twin active. Birth whether he or she?

Hello doctor,Iam having twin 3.5 month old baby one female & male.When I was pregnant twin 1 has prominent left cerebral ventricle in brain & EIF seen in both left & right ventricles.But after 1 month of my scan doctor said nothing to worry ab it because the brain ventricles are not developed it retains to normal size.After birth we have done brain,heart & kidney scan for both the babies it appears normal. As per the weight (male weight=2kg)all the impression seems to my male child bcoz when he born doctor said he is having thyroid,mild jaundice &  infection.In hospital twin A is represent female & twin B represent male babies.Now my twin B ( birth weight = 2.30kg) weight is 5kg & twin A (male)weight is also 5kg.But my twin A is active than twin B.Let me know when they in womb  who is twin 1 after birth whether he or she?