scientifically speaking, what happens physiologically to human males and females that makes them become parents?

i realize that a lot of children are conceived by parents who have not gone through this transition already. however, i have found that there are many couples who, sometime in their 30s, start getting an urge for having children. not even sexual. and not even just that thing women do where they freak about about their fertility. i'm talking about some parental instinct that happens for both women AND men at around age 30-32.

it's undeniable that this happens. so my question is -- why does it happen? can i do anything to not be a slave to my instinctive impulses?

related video:
https://youtu.be/12Z6pWhM6TA