Eskimo Brothers...two guys who have shared the same igloo so to speak.
Cyclops and Iron Man are Eskimo Brothers...both have slept with Emma Frost.
Iron Man and Daredevil are Eskimo Brothers...both were with Heather Glenn.
Hawkeye, Iron Man, Magneto, and Hank Pym all slept with Wasp.
Hawkeye, Dr. Faustus, Noh-Varr and possibly Graviton and Helmut Zemo slept with Moonstone.
Human Torch, Nova and Nova's Friend Bernie Dillon...all slept with Namorita.
Eskimo sisters examples: (I don't know of a better term even though Eskimo Sisters doesn't quite work...Harpoon sisters?)
Namorita, Gamora and Laura Dunham slept with Nova.
White Queen, Jean Grey, Maddie Pryor and Lee Forrester...Cyclops.
Sif, Amora, Jane Foster...Thor
Mockingbird, Wasp, Moonstone and one Scarlet Witch fembot with amnesia....Hawkeye.
Namor, his human nephew Leon, Naga and his son Merro...Llyra.
And some different sex Eskimo siblings...
Grey Hulk, Moondragon and Rick Jones...Marlo Jones.
Thor, Marlo, and Phyla-Vell...Moondragon.