stonStark, sometimes we (okay, I admit I'm often the we) postulate unfounded theories.
Duncan Targaryen
Targaryen Family Tree ~ Tower of the Hand was the older brother of Jaehaerys II Targaryen who was the father of Aerys II "the Mad King" Targaryen who was the father of Danaerys Targaryen. I just made the stuff about Varys up. But a year ago or so, I posted (Lord knows in which thread) that Varys might be a nickname for Viserys, sort of like how Dany is for Danaerys. What if the old spelling was Visaerys?
Vis
ae
rys What if an unwanted son, or a political embarrassment, or a presumed stillborn were spirited away and raised elsewhere? What if that child returned with some unknown agenda? The only things we know about Varys personally are what he told Tyrion... we have no idea if that information is the truth.
In another lost thread, I theorized (I don't know if I was the first or not) that Tyrion might be the ******* of Aerys II and Lady Joanna Lannister (Tywin's wife). First, Tywin was Aerys' Hand, but for some reason he quit. When it was obvious that Robert was going to win, Tywin sacked King's Landing. He did not merely gain possession of the city for Robert, he allowed his men to murder, rape, and pillage the capital city! Why? I think Tywin wanted vengeance, not because Aerys was a jerk, because he suspected Aerys of having relations with his wife. Second, We know that Aerys was crazy enough to rape his own wife... so why not someone else's wife? Third, Tyrion's physical deformities might be the product of inbreeding... as the Targaryens did. Tyrion's blonde hair is almost silvery white like many of the Targaryens. Tyrion's eyes are mismatched, green and black... black is not too far from deep purple. Fourth, Tyrion is fascinated with Dragons. Tyrion figured out how to use the Targaryen Pyromancers to burn Stannis' fleet. Tyrion once told Bran something to the effect, "On horseback, you'll be as tall as any of them." I think that Tyrion secretly desires to ride dragonback and be taller and greater than anyone.
Anyway, there is no real proof to these theories, just speculation.