Regarding Madara's Eternal Mangekyou Sharingan, there are three canon stories on how he obtained it.
The first version is mentioned by Itachi, while explaining the Mangekyou to Sasuke. In this version, he tells that Madara took his brother's eyes. Itachi shows the scene to Sasuke through Genjutsu, where Madara places his fingers over Izuna's eye and Izuna is surprised by the action. This would mean a forceful extraction.
The second version is told by Obito, acting as Madara. He explains to Sasuke that Izuna willingly gave his eyes to him (Madara), to protect the clan from the dangers of the fame.
The third version is told by the First Hokage, Hashirama Senju, when he was reincarnated by Orochimaru. He tells that Izuna succumbed to the wounds (during the warring period) caused by Tobirama Senju. And it is assumed that Madara took his brother's eyes after he died.
So which version is the actual one? Or is it a mix of all three?