Question: It is my father’s yahrzeit on Sunday, though there is another avel in my shul. Can I make a separate minyan on Motzaei Shabbos in my home?
Answer: The Gemara (Berachos 6a) teaches that tefilla is best accepted when davening in shul. One who chooses not to daven in their local shul is considered to be a ‘bad neighbour’ (ibid. 8a). Rambam (Tefilla 8:1) and the Shulchan Aruch (OC 90:11) codify this Gemara as halacha, though the Magen Avraham (90:15) adds another reason. The Gemara (Berachos 53a; Yoma 70a; Megilla 27b, et al.) teaches that berov am hadras melech, it is preferable to perform mitzvos with a large presence. Therefore, even when one can daven with a minyan in their home, one should still go to shul.
The Mishna Berura (90:38) adds that one should strive to daven in shul even if there is no minyan there. While one may not be considered a bad neighbour, nonetheless, a home minyan is not ideal as davening in a shul (See Shaarei Teshuva 90:4).
R’ Moshe Sternbuch (Teshuvos Vehanhagos 1:127) writes that berov am hadras melech is both a mitzva and a zechus, which takes precedence of the minhag for one to daven on a relative’s yahrzeit. While splitting the minyan into two would accommodate two chiyuvim, that would not justify davening outside of a shul.
In conclusion, one should rather daven in shul rather than a minyan at home, even if it means not being able to be chazzan on a yahrzeit. Indeed, the Gemara (Berachos 8a) teaches us that being meticulous to attend shul properly leads to long life.