Prince of Persia: The Forgotten Sands/WMG

Malik from Forgotten Sands is The Mourning King
Both of them look pretty similar, and wear similar clothes/armour. All we see of Malik at the end of Forgotten Sands is him collapsing. He went into some sort of coma, and when he woke up, didn't tell his family that he was still alive out of shame and embarrassment at his possession. He fled to another kingdom, eventually became its ruler, and this led to the events of the 2008 Prince of Persia game.