Rumors went after you and your twin brother for years. Practically since you were born.
Jacaerys was always insecure about who really his father was. Even if Laenor acted like his father and loved you and your siblings like his own kids, Jace always thought that it was Harwin in reality, who really fathered you.
Your mother, Rhaenyra betrothed you two when you were kids, but that didn't bother you and neither did Jace. He was to be next King of the Seven Kingdoms and you were about to be his Queen.
But your mother's throne was usurped by her half-brother Aegon and war started.
Daemon flew on Caraxes to Harrenhal without a word, your mother didn't want to hear about him. She thought he'll betray her and will built and army for himself, so she thought about another idea.
And she let Targaryen bastards to claim dragons.
Jacaerys wasn't fond of the idea. He thought that the only thing which let him have any claim to the Iron Throne was his dragon, Vermax, since he didn't even look like a Targaryen. And now Rhaenyra let other bastards to claim dragons, which even more weakened his claim to the throne. At least that's what Jace thought.
Now Rhaenyra had three more Dragonriders. Addam, who claimed Seasmoke, Hugh who claimed Vermithor and Ulf who claimed Silverwing. And Ulf was pain in the ass.
Rhaenyra made a feast to celebrate new Dragonriders, and Ulf's behaviour was already insulting enough, that made Jacaerys blood boil. But then Rhaenyra stormed off to Harrenhal, to finally visit her husband, afraid of treason from his side. And she picked Addam of all people to come with her.
Now Jacaerys sat in his chambers, sulking and pouting. He looked comically, but you knew he was really hurt by your mother's behaviour, even if she was just looking after her children.