Which parent determines the sex of their child? – It turns out that it’s mostly up to the man?if you ARE the dad! It may also depend on whether or not dad smokes.
Researchers found that men were more likely to have sons if they had more brothers (and vice-versa if they had more sisters). The same link was not found for women.
Basically, the woman provide the X chromosome (people with XX are female). The male can provide either a Y or another X (and people with XY chromosomes are male).