consider the following

Graystripe gets too much flack for his choices in mates. Like, come on. Everyone's out here marrying their cousins and uncles and whatnot. Graystripe said "Alabama? Don't know her" and had kits with Silverstream from RiverClan and Millie, a non clan-cat. Makes sense, because briefly the official family trees said his parents were siblings(patchpelt and willowpelt... oof). That's gotta be strange.