My mother was Niftar 2 years ago on the 20th of Adar (it wasn’t a leap year). I wanted to know when to say Kaddish this year (on a leap year). My rabbi told me adar I, my father’s rabbi told him adar ii, my brother’s rabbi told him to say it both adars. Is there no definitive answer for this? Since I go to my father’s shul for nightly services, should I say kaddish according to his rabbi’s rules in that shul, but when when I go for morning services to my shul, then say kaddish according to my rabbi’s rule in my shul. To further complicate things, my brother is visiting me this Shabbat - what should he do? We are all VERY thoroughly confused.
Your question is a complex argument amongst the Poskim as it is a matter of Minhag. Therefore, you should pick one Rabbi of the three and act as he said. Most Ashkenazi Poskim Pasken that you are to say Kaddish on the Adar Aleph and the Spharadi Poskim on Adar Bet (relevant only in a community without a Rabbi!). Best Wishes, Rabbi Zalman Baruch Melamed