What?! Impossible to start a family at 18 and also enjoy mathematics?

Not everyone who has unprotected sex at 18 (or with an 18 yr old) is some numbskull just going at it for unscrupulous pleasure.

(As another reply also pointed out: the pun was crafted by the OP’s dad, not the 1yr-old’s dad; and OP could be the child’s mum or dad)