Warning: Possible spoilers ahead.

First, we're familiar with the theory known as R + L = J. The theory concerns who Jon Snow's father is.

Which would make him the niece of Daenarys, and actually a Targaryen.

According to another fan theory, another character has Targryen blood too.

Could Tyrion Lannister be a Targaryen? The theory is based on the books. Daenerys' father, King Aerys, was infatuated with Tywin's wife Joanna. 

He wanted to bang her first at their wedding, because you know, he's a dick plus he's the king. Which he apparently did take advantage of, so much that it could have resulted in Tyrion. 

Which could explain why Tywin hates Tyrion so much. He's even been heard saying to him, "I cannot prove you are not mine."

Tyrion may be a dwarf, but he's got balls of a dragon.

In the books, his description seems closer to a Targaryen than a Lannister. He's also got a morbid fascination with dragons and knowledge.

According to the prophecy in the House of the Undying given to Daenerys: "The dragon has three heads."

Which could make Jon, Dany and Tyrion the three heads?

There's also the theory that a dragon must be born of blood. All three of them had their mothers die while giving birth to them.

When Tyrion shot Tywin, he said that he had suspected he wasn't his son for many years. 

Of course, that didn't deter Tyrion. 

Does this sound like a believable theory?