There are two Purple People. William, who we see in FNAF4/FNAF3/hear about in FNAF2/1.
Michael is not really known about until FNAF4 as the Bully Brother, and in SL as the character we play as.
Michael becomes a LITERAL Purple Man after he dies, decays, and becomes mummified.
William is purple symbolically. He's not dead until the cutscene in the Spring Bonnie suit.
William returns as Springtrap in FNAF3 and FNAF6. Michael is scooped & killed in SL and inhabited by Ennard/their Sister.
Ennard leaves, Michael is re-animated by their own soul and continues "living".
William does not have a father shown anywhere in the series. William IS the father, to the Bite Victim, Ice-Cream Girl, and Michael.
The ending messed with as all because it seemed like Springtrap was talking... but it was Michael narrating, and Springtrap popping out in response.
Not Springtrap = Michael because Michael was talking and Springtrap happened to be there.
Michael was already talking and Springtrap appeared at the end to show Michael's goal: his father survived the fire.