Sasuke is a Child of the Uchiha and thus a Child of the Father of all Uchiha (Madara)on the last page Madara said that he would sacrifice his own child to achieve his goal. It's pretty obvious he was referring Nagato.
"be it close friend, brother or even my own child"
Madara killed his friend to obtain MS. Check
Madara took his own brother eyes and obtained EMS. Check
Madara gave rinnegan to Nagato to revive him in future. Check
Pretty obvious.
You can call your descendance :"child".You could say the child of the child of the child......of my child.Reading comprehension fail. Why would Madara call Sasuke his child? It doesn't make sense
No. Sasuke has nothing to do with Madara. Get over itHe's actually talking about Sasuke. Meaning Sasuke is madara's great grand child
Obito called Madara his ancestor [It would make more sence if Obito was his grandson. And no, he isn't
30-35 not 40-50:XNagato is around 40-50 while Sasuke is 16. Who do you think has better chance to end up being Madara's son?