I am learning hilchos kiddush and I came across a halacha that I never knew before. If a man on Shabbos day hears kiddush in shul and has mezonos and his wife didn’t hear kiddush, could he be motzi her in kiddush? It would appear based on reading of the Mishna Berurah in 273:20 that she should make kiddush if she knows how to. And since kiddush at day time m’ikar hadin is just the bracha of Borei Pri Hagafen (Pri Megadim AA 289:2) if she is able to make hagafen when she drinks grape juice during the week, she could also do it on Shabbos. Is it better for her to make the bracha if she comfortable with it (i.e. there are no guests around)? However, the minhag of the velt seems to be that the husband is motzee the wife.
What if someone who did not hear kiddush is eating by someone who did eat mezonos at a kiddush but is machmir like what Rav Moshe Sternbuch says and I heard quoted from Rabbi Shlomo Zalman and others to make kiddush again before the seudah on pas. The host’s kiddush is just a chumra, but the guest has a full fledge obligation to make kiddush. Should the guest make his own kiddush if he able to (assuming the baal Habayis won’t get offended or if he offers the guest to make kiddush)?
It is true that if one was already yotza Kiddush that it is better if the person that still hasn’t heard kiddush say it himself. However this is only a preference, because the halacha is that one may be yotza someone else even if the other person knows how to make Kiddush by themselves. The MIshana Beriura says this is sief katan 20, and in the BUir Halcha D:H V’hu, that even in this case it is “mitzvah b’alma l’chatchila”. Also see Shmiras Shabbos Khilchoso 51 ftnt. 13 “that the minhag haolam is to meikil with this, and one should not be moche if someone does it because that is the ikar halacha”. If the host will offer you to make your own Kiddush you can take him up on the offer to make your own kidddush.