GEN1570 [Why not of his grandfather, Abraham?]   Regarding the question of who is covered by the commandment to honor parents, there may be some surprises.   In-laws are covered … Mekhilta de Rabbi Ishmael, “Yitro”, ch. 1, p. 190; Yalkut Shimoni, “1 Samuel,” no. 133; Shulchan Aruch, Yoreh Deah, 240:24.   In the case of a divorce, a step-parent is covered, as long as honoring the step-parent does not detract from honoring the natural parent. Because the main activity of Jewish parenting is pedagogic, the obligation to honor parents is extended to teachers.   According to the Talmud Ketubot 103a, older siblings are covered as well. Surprisingly, on the question of whether grandparents are covered, there is a difference of opinion.   Despite the Talmudic saying that “one’s grandchildren are like one’s children,” Yevamot 62b; Kiddushin 4a, this view was not universally held. E.g., Sotah 49a  The reason is psychologically interesting. The major work of the Jewish mystics, the Zohar 2:233a , states, “a man loves his grandchildren more than his children.” In other words, because grandparents tend to dote on their grandchildren more than on their own children, there was an apprehension that the bond between grandparents and grandchildren might threaten the relationship between children and their parents Genesis Rabbah 94:5; Rashi and Nachmanides’ commentaries this verse. Hence, the grandparent-grandchild relationship was deflated by some of the sources in order to try to defuse this possibility.  HTBAJ 166