I was clowned for saying this but Minamoto is on to something, Sasuke has a thing for girls with Senju feats and at one point only respected individuals with power during his blood thirsty phase.
Incarnates share similar personalities, it wouldn't be a stretch to say Madara had a thing for Mito because he may share the same preferences for women as Sasuke. Kishi loves parallels so it's likely they may have been a love triangle between the incarnates and Mito at one point.
In Madara's eyes, weak women are ugly but Mito had the ability to rival his control over bijuu and was blessed with high life force even for Senju standards. Madara isn't Nagato's biological relative but he definitely had a role in Nagato's upbringing and imo it's because Mito inspired him to rely on her clan's power.