Which members of the Targaryens were featured in Game of Thrones?

In addition to Daenerys and Viserys, Aemon Targaryen (Peter Vaughan) appeared throughout the series. Known as the last known Targaryen in Westeros, he was the great-uncle of Daenerys and Viserys. 

In the season seven finale, it is finally revealed that Jon Snow’s (Kit Harington) father is Rhaegar Targaryen (Wilf Scolding) and that his birth name is Aegon VII Targaryen, making him the heir to the Iron Throne and Daenerys’ cousin. 

Why is the House Targaryen family tree so intertwined?

Well, simply put, they really liked to marry each other.

According to Game of Thrones, the family had a reputation for inter-marrying siblings in an effort to keep the bloodline pure. 

This desire for purity caused some problems further down the line, as the inbreeding sometimes produced, err, genetic issues, for lack of better words. “Madness and greatness are two sides of the same coin,” Lord Varys (Conleth Hill) said of the Targaryens in season eight. “Every time a new Targaryen is born, the gods toss the coin in the air and the world holds its breath to see how it will land.”