Q. (I have a relative who is dying. Unfortunately, he is married to a gentile…) And assuming he does not leave his wife before his death and insists upon being buried next to her (she is still alive), do the laws of mourning and kaddish remain the same as any other dearly departed?

A. As mentioned in the previous answer no shiva and mourning are observed for the ones who willfully abandoned the Jewish community, converted to another religion or intermarried with Gentiles, ( Shulchan Aruch Y.D. 345: 5,) unless they openly repented before they died. (Remoh Y.D. 340: 5, Chochmas Odom 156: 3)

Although today it is customary to mourn for non-observant relatives since they are considered “Tinok Shenisbah” or being unknowingly or non-consciously unreligious, however, intermarrying as converting to another religion are extreme acts that almost everyone would accept as willful and deliberate. (Tzitz Eliezer 13: 94, Yalkut Yosef – Avelus 14: 13, Shevet Halevy Y.D. 1: 165)

Some Poskim mention observing avelus for one hour, (Yalkut Yosef Avelus p. 302, Ma’ayan Omer 84) however, they stress that this may depend on unusual circumstances and a Posek should be consulted in every case.

Besides this last Halacha, Horav Shlomo Miller’s Shlit”a opinion is similar.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a