Who May Say Kaddish Yasom?
Kaddish Yasom is recited by a son on the yahrtzeit of his father or mother, and during the year of mourning. In case there is no son who can say kaddish, other male relatives should say kaddish instead. Of course, friends may do a chesed for the merit of the neshamah by doing mitzvos, learning Torah, and giving tzedakah in its honor. If a person wants to say kaddish for someone who is not his father or mother during his parents lifetime, he has to make sure that his own father and mother are not makpid, do not mind that he is saying kaddish. Learning Torah, Mishnayos, giving tzedakah, doing mitzvos, as well as being a shliach tzibur, davening at the amud (without reciting kaddish yasom), in honor of the neshamah, are perfectly fine even if the person’s parents are still alive. Indeed, davening at the amud is a great zechus for the neshamah.