http://revach.net/article.php?id=3111

Section: Halacha   Category: Tshuvos
Shevet HaKehosi: Who Will Be The Sandak, Your Father Or Father-In-Law?
Rav Shammai Kehos Gross was asked (Shevet HaKehosi 4:234), if someone is making a Bris and has a choice to give the honor of being the Sandak to his father or father-in-law, who should he give it to?

He says that if there are no other outside factors weighing on the decision (and there usually is), you should give it to your father because of the mitzva of Kibud Av.  Although the Shulchan Aruch (YD 240:24) paskens that you must honor your father-in-law, the Shach says that this chiyuv is only MiDiRabanan and at most you need to honor him like we honor respected elders, but not because of Kibud Av.

The Sefer Chareidim implies that honoring one's father-in-law is Min HaTorah and is a chiyuv just like Kibud Av.  However says the Shevet HaKehosi, still honoring your father is more important because he is written specifically in the Torah, and the chiyuv of a honoring your father-in-law is subject to the above dispute.

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.

This article has not been reviewed by the posek of the AskRevach section, Rav Peretz Moncharsh. Any questions regarding this topic and Halacha L’Maaseh may be asked to him at www.revach.net/ask