Oh, we are so circling in on a parallel. Not just in jaceaegon but in the whole family.
Alicent’s children look like Targaryens. They have the silver white hair, the purple eyes (in the books), the sharp angles and ethereal bone structure of Old Valyria. At first glance, they are all a Targaryen should look like.
But their dragon eggs didn’t hatch. Out of four children, only Daeron’s dragon was his cradle mate, and he’s by far the least influenced by the family since he’s sent to Oldtown at a very young age. They don’t know complex Valyrian or the right conjugations, their pronunciation is either wrong or they straight up don’t know how to say it (exhibit A: Aemond’s mispronunciation and incorrect usage of the word taoba when it should have been taobus. Exhibit B: Aegon doesn’t speak to Sunfyre in High Valyrian when he commands him). They don’t wear the colors of their house - they always wear green instead of red and black - and they don’t pray to the Fourteen Flames, which is the traditional religion of Old Valyria and the gods the Targaryen pray to.
Alicent’s children may look Targaryen. But look is all they do.
“The only thing that makes you different than the common folk is your tainted dragon blood,” Lucerys sneers, a nasty thing in an otherwise pretty face.
Rhaenyra’s children, on the other hand, don’t look like Targaryens. They have their pretty faces and ethereal beauty, but their hair and eyes are as brown as the earth, and the shape of their faces far resembles the one of a certain strong soldier, rather than an experienced sailor. In a family full of exotic beauties, they look much closer to the sons of the First Men.
But their Valyrian is flawless. They’ve learned and they’ve trained until it rolls off their tongues more naturally than the common tongue does. Their dragon eggs all hatched in their cradles, the bonds they have with their dragons is incredibly deep. They pray and call to the gods of Old Valyria, they honor their family’s traditions. Their red and black clothes proudly display their true allegiance to their house. They know their history, how they escaped the doom and why they are hailed as kings in this land. They also know the little things, the small rites and the lullabies to calm down the dragons, the ones they were sung from a young age because they are also dragons. The Velaryon children may look Strong, but they are Targaryen in every way that matters.
In the end, Alicent’s children were raised by common men, and Rhaenyra’s as true Targaryens. The way they behave and their priorities are clear depictions of that.