King David, may he rest in peace, called Saul, his father-in-law, "father", as it says, "My father, see indeed". Our Sages, of blessed memory, said - concerning Jehoshaphat, King of Judah - that whenever he saw a Torah scholar, he would rise to his feet, and embrace and kiss them. The Gemara asks: How could he do so? Is it not written "Appoint over yourself a king" of whom you are to be in awe? The explanation is that he did not do so in public…
Yet we are obliged to say that what the Gemara says on this entire matter – what a king must not do in public – applies to all other people, but not to one's father, such as Solomon, who ruled while his father was alive…also, Moses bowed down before Jethro and embraced him in public, despite that he was only his father-in-law, which teaches us that one's father-in-law is to be respected like one father.