That would result in a “split” yartzheit!
Only scenario which can lead to a split Johrzeit is someone passing away in an Adar Poshut, and according to some opinions in leap years, s/he may have to observe both in Adar Rishon & Adar Sheni, but even then, only one time can s/he have Kedimo over other Aveilim, since intrinsically a Johrzeit can only be once.
Likewise for someone who passed away on marCheshvon 30, Kisslev 30 or Adar Rishon 30, depending on what transpires the following year [by marCheshvon 30 & Kisslev 30], may have a split Johrzeit, but again can only one time have Kedimoh over other Availim.