In “Clone Wars”, Satine and Obi-Wan had something very close to a love interest (we understand that there was something between the two of them a few years prior to the Clone Wars, when Ben was a young adult I believe). Besides Satine had a far younger redheaded sister. Could she be that very child hidden from Ben as a pretended sister ? But I agree it wouldn’t be very convaincing she had a child without Ben knowing it, and that Rey is Ben’s grand-daugther. But if someone wants to elaborate over Rey being a Kenobi this is the only thing I can think of right now.