In human being, the sex of the individual is gentically determined. i.e., the genes inherited from parents decide whether it will be boys or girls.
Most human chromosomes hve a paternal copy, and we hve 22 such pairs. But one pair, called the sex chromosomes, both called X. But men have a mismatched pair in which one is a normal -sized X while the other is a short one called Y. So women are XX, while men are XY. All children will inherit an x-chromosome form their mother regardless of whether they are boys or girls. Thus , the sex of the children will be determined by what they inherit from their father. A child who inherits an x-chromosome from her father will be a girl, and one who inherits a Y-chromosome from him will be a boy.
