Q. A person who is already saying Kadish for his father-in-law, (as there are no sons), was asked to recite Kadish for another recently deceased relative, who does not have anyone to say Kadish in her name. Can he accept this additional commitment and now recite Kadish for two Neshamot instead of one at the same time?

If it is permitted to say Kadish for two, does he have to be matir neder?

A. Many Poiskim agree that one Kadish could be said for a number of deceased (Rana”ch 1,77 – Gesher Hachaim 1, 326,7 – Kol Bo p.376, Tzitz Eliezer 7,49, et al.). However Igrois Moishe (Y.D. 254) and Doivev Meishorim (2,14) at least partially disagree. The fact that no contracts or monetary rewards are involved in this case is also favorable. Igros Moishe (ibid.) advises that at least one Kadish a day should be dedicated to each niftar. So too is the opinion of Horav Shloimo Miller Shlit”a. He recommends thinking in advance for whom this kadish is to be recited; the rest should be said with the intention for both.

No hatoras nedorim is required, moreover the declaration of Kol Nidrei or Mesiras Moido’o on Erev Rosh Hashono, would make it unnecessary.

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