My understanding is that the general ranking to daven for the amud when their are competing requests among “members” of the shul i as follows:
1.Person within Shiva
2.Person having Yartzeit
3.Person within Shloshim
4.Person within year of Aveilus
This presumes the competing parties both are saying kaddish for a parent (mother or father). I have heard mentioned, but have not seen a source, that for two otherwise equally ranked persons seeking to daven, a shiva or yahrtzeit for a parent takes priority over that for a sibling or child.