Hmm...I've actually thought about this, though I have yet to put it on paper. logically, noble bloodlines should indeed focus on refining their hereditary gifts- after all, blue blood existed in real life, it would only make sense for it to be even more of a thing here. Though ideally, they shouldn't have to rely on incest >.>
I would suggest that most sorcerers don't come from a stable lineage, but rather manifest spontaneously from some lick of blood from their ancestor's manifestation- it is unlikely that they will pass it down unless they go out of their way to strengthen their bloodline. However, the rare few that do have a bloodline that can be passed down are highly prized marriage partners among the noveau nobility, as it's their ticket to becoming a 'true' noble house.
Here is an example, using the now named House Getandmark.
Bloodline: House Getandmark
Direct members of the house are tall and burly, with fair skin, bluish-silver hair and grey eyes. Descendants of the Sovereign of Sharks, Sen'zawr, they primarily possess Altasian endurance that allows a fully-fledged knight of the house to fight for a full week without rest in armour twice as thick as regular plate, though among their more minor traits are heightened strength, speed and affinity to the water element.
It is said that exceptional members of the house can manifest the legendary Crest of Sen'zawr.