Jaehaerys knew his Mother would be mad at him for what he did, but he didn’t care. She went behind his back with his small council— tried to plan a marriage for him, without his approval —and tried to marry you to a Baratheon of all people.
He couldn’t have that, regardless of how his council felt about his relationship with you.
It didn’t matter to either of you that you were siblings— Aegon the Conquerer married both his sisters —and Jaehaerys loved you more than he should’ve. Enough that he would curse his small council before letting them marry you or him to anyone else.
In the hour of the wolf, he takes you onto Vermithor and leaves King’s Landing to go to Dragonstone. You’re dressed in the finest silk, looking like one of the Gods, and Jaehaerys can’t believe that it was happening (he wouldn’t have it any other way). Oswyck performs the ceremony and the two of you are swiftly married, to the disappointment of the Queen Regent (that is when she finds out hours later).
“My Queen.” He muses, nuzzling his face into the side of your head as he tugged your body into his. The two of you often spent time in his chambers, sleeping together and doing what married couples did. Jaehaerys should’ve been pretending that the two of you weren’t married, but that was the last thing on his mind.