From A Wiki of Ice and Fire
|Theories may be removed if ...|
- He himself claims to be a bastard of House Lannister.
- Tywin is known to have sex with prostitutes, as with Shae.
- He has physical and characteristic similarities to other Lannisters of Tywin's line.
- When asked if Tywin had any bastard offspring, George R. R. Martin merely answered that "[Tywin]'d have you flogged for the mere suggestion."