How do you educate your boys related sex? (Giving sex education to male) and male single parent to their daughters.

It is surely talked much about on internet "Indian education not teaching and giving sex education" and "'sex' is taboo as whole" Now back to question... As for girls it can be said that her mother can help when her periods starts and further. >I would also like to know how single male parent does in this situation? How do (you as) parents will teach their male child about sex? How do you proceed and make point to them about it?