Daeron the Good's Fatal Mistake Episode 4 of the First Blackfyre Rebellion explained 

The reason why Daeron treated his half siblings well is probably because he was raised well by both his mother and his uncle.

HOUSE BLACKFYRE IS THE TRUE ROYAL FAMILY AND HOLDERS OF BLACKFYRE THE SWORD OF KINGS🗡

im making my way through your agot reread (which is excellent, way better than jacob preston's if i may say), can i just suggest you look up the right pronunciation for brazier, as you pronounce it as brassiere, which makes it unintentionally hilarious :-)

I love Daeron II, he is in my opinion probably the best Targaryen King Westeros ever had (with egg being a close second) finally a Targaryen who is not into incest and his move making his heir marry the daugther of a Stormlands Marcher Lord to sort of balance out the dornish influence is genius. Like saying "yes im bringing my wife who is a Martell along other dornish men to my small council but my elder son and heir is marry to a Dondarrion, so when he gets the Iron Throne and afterwards their elder son (Valarr) it is hoing to be your turn".