I was a bit wishy washey on id'ing them until I looked veeeery closely. You actually have more than two varieties. One of your little light colored ones is a golden comet/sex-link. You can tell because she'll have two little caramel colored racing stripes down her back.
The other two buffs are hard to tell, if I had to put money down, I'd say Buff Orpingtons. (not RIR, those look completely different, and MUCH darker coloring with almost barred wings coming in at first).
The blacks are most likely black sex links. There is a possibility that like the buffs, you have more than one variety, and have both Australop and Black sex links.
Your extended family has good taste in laying birds, even if they had no idea what they were doing when they bought them!