The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Vayelech (listen to audio recording for precise citation), writes that just before the onset of Yom Kippur, before one goes to the synagogue, he should kiss his father and mother’s hands and ask them for forgiveness. Requesting forgiveness from one’s parents before Yom Kippur is, in the Ben Ish Hai’s words, a “Hiyub Gadol” – “great obligation” – to the extent that one who does not ask his parents for forgiveness is considered a sinner and belittles his parents’ honor. The Ben Ish Hai explains that if Halacha requires asking forgiveness before Yom Kippur from anybody one may have wronged, then this is certainly obligatory from one’s parents, given that nobody perfectly fulfills the obligation to respect parents. The Misva of honoring parents is especially demanding, and all of us are guilty, to one extent or another, of failing to show our parents proper respect. It is therefore critically important to ask one’s parents for forgiveness before the onset of Yom Kippur.
If one foolishly does not ask his parents for forgiveness, the Ben Ish Hai writes, then his parents should nevertheless grant him forgiveness. They should say explicitly that they grant their child complete forgiveness for whatever wrongs he had committed against them.
The Ben Ish Hai adds in this context that a husband should grant his wife forgiveness before Yom Kippur for overspending during the year, and that if one’s Rabbi lives in his town, he should visit him before Yom Kippur to ask forgiveness for failing to treat him with proper respect.
Summary: One is obligated to ask his parents for forgiveness before Yom Kippur, for failing to treat them with proper respect. Given the strict demands of Kibud Horim (honoring parents), there is nobody who truly honors his parents as required, and therefore everyone must request his parents’ forgiveness before Yom Kippur.