As both Aenys and Maegor took multiple wives, and one of Maegor’s wives was actually Aenys’ daughter, we can bet we’ll see even more of why the Targaryens are the only family of the Seven Kingdoms with more inbreeding and drama than the current generation of Lannisters.
Aenys I and Maegor the Cruel have been mentioned in the show and the books, but most of their history is unexplored.
Some of George R.R. Martin’s other stories have established that the two brothers both married sisters, so there will definitely be some overlap in the “wives” and “sisters” categories.