This video takes a great look at the endings (there are many) of the game, and has a ton of spoilers. Not something that affects my ability to still enjoy the game, but if you're enjoying playing through it and discovering the new characters and endings, this video isn't for you.
But it is deep, and good :)
The Binding of Isaac is already pretty dark already but this video really focuses on it and doesn't sugar coat it. It's nice to see it all laid out as I doubt i'll spend time getting all the endings.
That said, I feel sad for the kid. What a horrible way to live.