Well, it took me a while to come to this realization, but my question is, who was the catalyst for Madara/Izuna's mangekyou sharingans. We know now that the stressful/life changing event causes a mutation of the eyes: giving us a sharingan.
and then we know witnessing/killing someone extremely close to you when you have your sharingan unlocks the magekyou.
Ok, so who was it that triggered Madara and Izuna's MS. could it be their dad? because here it states that he was now the head and he had the EMS.
oh and orochi has senju cells... seems he really changed course instead of just obsessing over the Uchiha