The problem is you are thinking the guy wants her parents money.

That's because the guy's parents are feeling entitled that her parents should pay for the whole wedding. And the guy also said they should pay more than double his share .

I have already mentioned in the post, that as he has less money, he should decide upper limit on expenses.

What that girl probably means is if he can't be a fifty percent partner now, will he always live off wife's money by saying his money belongs to his parents and sister for her wedding, buying house for parents. Will he always tell his wife and her parents to take care of his household and child expenses because he has responsibilities to sister and her grand wedding party and could not bother to make a basic emergency fund for himself?

If the girl's parents are insisting on lavish wedding, then he should not agree to that- he should say this is all I can contribute and she should match that.