This will prob sound like a weird one: to mum's with babies to different fathers- was their much of a difference between the birth weight of your babies?

I have read somewhere that birth weight is determined by the mother (???)

DS (my XP's son) was 7pounds 2oz. XP is 6ftish and average weight.
DH is only my height (5'9) and average weight. I am tallish for a female (I guess) and average weight.

So, does any of this matter or is it a lucky dip?