[TWOIAF Spoiler] Targaryen Lineage

[Mithras]

After fighting the third Blackfyre Pretender, I am sure that whatever doubt Maekar had about Bloodraven should have been washed away.

[Lord Varys]

That would have been much sooner, in my opinion, as it is implied that Aerys I named and installed Maekar as Prince of Dragonstone in 217 AC, after Aelor's death. That was two years before the Third Blackfyre Rebellion, and with Maekar being the acknowledged heir at this time everything should have been fine.

Thinking about that, here is a speculated list of all the Princes of Summerhall:

1. Prince Maekar, named by Daeron II after he had the castle built.

2. Prince Daeron the Drunk, installed by Maekar, after Maekar himself became Prince of Dragonstone in 217 AC (that is confirmed by the fact that Daeron preferred to be styled Prince of Summerhall even after he had become Prince of Dragonstone).

3. Possibly Prince Aerion, after Daeron became Prince of Dragonstone when Maekar ascended the Iron Throne in 221 AC.

4. Prince Aegon when Prince Aerion became Prince of Dragonstone after Daeron the Drunk died.

5. Princes Jaehaerys and Duncan respectively. First Duncan was Prince of Dragonstone and Jaehaerys the younger son who might then have Prince of Summerhall. After Duncan gave up his rights, Egg most likely named him Prince of Summerhall in Jaehaerys' place. Depending on Jaehaerys' health there is also a certain chance that Egg gave Summerhall to Daeron instead of Jaehaerys.

[Mithras]

How about Rhaegel?

[Lord Varys]

Well, Maekar was the Prince of Summerhall in THK. Daeron II had given it to him, I doubt Aerys I took it from him and then gave it to Rhaegel shortly before the latter's death. Summerhall seems to have been a present of Daeron II to Maekar specifically.