Who were Muhammad's kids?

Answer 1

That is a HUGELY complicated answer, but to simplify, the only child you need to worry about is Fatima. She is the daughter of Prophet Muhammad with his first wife. The schism in Islam between Shia and Sunni Muslims is that Shia believe Fatima and her descendants are the true heirs or sharifs.

The Prophet may or may not have been married several times after the death of his first wife, but it is speculated that those marriages may have been a mixture of political alliances or an act of charity for widows in a culture that didn't value non virgin brides whatever the reason. It is not know if those subsequent children were step children from first marriages or children they had together in the second marriage.