If your son-in-law is good, you gained a son. if he is bad, you've lost a daughter. (Hebrew Proverb)
Till age six, your son is your master; until ten he's your servant; until sixteen, a wonderful adviser; from then on, he's either your friend or your enemy. (Hebrew Proverb)
Don't put your trust in princes, or the sons of men; there is no salvation in them. (Hebrew Proverb)