To me, Rhaegar was clearly displeased with Aerys II killing Rickard and Brandon Stark.
We all know he meant to call a council, using the Tourney of Harrenhal as a disguise. Yet he hesitated; maybe Aerys II's presence made him step back. But, when he talks to Jaime before going to battle, he doesn't see so hesitant anymore. He talks about it openly with Jaime even.
Rhaegar says it does no good to dwell on roads not taken, but I can see a hint of regret on him. Maybele he thought that, had he not hesitated on Harrenhal, Aerys II wouldn't have killed Rickard and Brandon, the Rebellion wouldn't have happened and so on.
Of course! I can’t believe it needs to be said that Rhaegar did care about Rickard and Brandon’s death, that he didn’t approve of his father’s action, that his hands were pretty much tied from the very beginning which is proved by GRRM’s own words. We really have to chew every aspect of his character and put it into antis’ mouth
