Line-breeding only works if you're willing to do some ruthless selection on the progeny; not ethical with humans in our world, and I really can't see either Tarvek or Vi going along with it even in the rather looser ethical universe of GG. Whatever the technical closeness of their cousinship, they look enough alike to be very close genetically, as you noted, whether through happenstance of drift or multiple generations of cousin marriage.
On the other hand, if the Mongfish could clean up Tarvek's genes prenatally; perhaps someone else also has that skill? That would make genetic problems moot.
Myself, I think neither Tarvek nor Violetta would be happy married to each other. Tarvek is considerably smarter than Vi (witness her inability to see past his previous mask, even with demonstrations) and I suspect that like Gil he needs a woman who can at minimum follow his ideas. Vi also doesn't share his interests (muses) or appreciate sparkiness (twisted courtship rituals) unlike Sleipnir's appreciation for Theo's sparkiness. Tarvek also goes so melty gooshy when he gets to snuggle Agatha, that I think he would want a softer more supportive type of relationship than he'd get with Vi. He's had enough of prickly difficult family, and I don't think he likes it.
She's a very straightforward girl, who likes pretty things and obstacles she can see how to overcome; Tarvek frustrates her no end and sets off her temper, which I don't think she enjoys either. She will be much happier with a non-spark fellow. I like her with Moloch because he has much the same straightforward solutions to problems; and I think he'd not provoke her temper nearly so much. Back to back in the service of her lady and his, clear goals and a path to get there; that's what Vi wants.
They do love each other under it all; I just really see it as a sibling relationship, not romantic in the least. One that most definitely is better with a fair amount of space available to get away from the other when needed.
Re: European Marriage Habits
On the other hand, if the Mongfish could clean up Tarvek's genes prenatally; perhaps someone else also has that skill? That would make genetic problems moot.
Myself, I think neither Tarvek nor Violetta would be happy married to each other. Tarvek is considerably smarter than Vi (witness her inability to see past his previous mask, even with demonstrations) and I suspect that like Gil he needs a woman who can at minimum follow his ideas. Vi also doesn't share his interests (muses) or appreciate sparkiness (twisted courtship rituals) unlike Sleipnir's appreciation for Theo's sparkiness. Tarvek also goes so melty gooshy when he gets to snuggle Agatha, that I think he would want a softer more supportive type of relationship than he'd get with Vi. He's had enough of prickly difficult family, and I don't think he likes it.
She's a very straightforward girl, who likes pretty things and obstacles she can see how to overcome; Tarvek frustrates her no end and sets off her temper, which I don't think she enjoys either. She will be much happier with a non-spark fellow. I like her with Moloch because he has much the same straightforward solutions to problems; and I think he'd not provoke her temper nearly so much. Back to back in the service of her lady and his, clear goals and a path to get there; that's what Vi wants.
They do love each other under it all; I just really see it as a sibling relationship, not romantic in the least. One that most definitely is better with a fair amount of space available to get away from the other when needed.