[drjimmy]

There’s a longstanding theory that Tyrion is the bastard son of Joanna Lannister (Tywin’s wife) and Aerys Targaryen (Dany’s father).

That would give an additional meaning to the title of the penultimate episode. While "Battle of the Bastards" refers to Jon Snow facing off against Ramsay Bolton, Tyrion was also involved in a battle, in Meereen.

In season one, Tyrion says to Bran, "I have a tender spot in my heart for cripples and bastards and broken things." I assume he was thinking of himself as a broken thing, but he might have unknowingly been talking about his bastard origins as well.

[Boogieman]

Yes, and he also said to Jon Snow “every dwarf is a bastard in his father’s eyes”. However, Tywin denied repeatedly that he hated Tyrion because he was a dwarf, and always said he thought he wasn’t really his son.

I think Tyrion just didn’t want to consider that possibility, since being a Lannister was the only thing that got him any respect at all in his world.