I am a convert B”H and married to a sefaradi, so we follow the sfarad and edot ha mizrach minhag. I wanted to ask about my biological family: what does the halacha say about a convert going to his father’s or mother’s funeral? What about grandparents? Am I permitted to go into the church, without touching or bowing to anything, just for giving the last respect to my biological parents–or is this not permitted? Thank you very much.
You may and should attend the funeral of biological parents. Although a convert is considered as a newborn babe, this does not mean that his biological parents cease to exist, and the basic obligation to honor those who brought you into the world and raised you certainly applies. However, you may not enter the church itself.
Sources: Many poskim write with great stringency about entering a Church, and Rashba expresses doubt even concerning entering in cases of pikuach nefesh (under such circumstances, however, Rosh explicitly permits entering). For a leading Sefardi ruling on a similar question, see (at length) Yabia Omer, vol, 2, Yoreh De’ah no. 11.