This!! Was this why Revan's heart could not decide if he needs to pursue his little crush??A joining between their two clans would be inappropriate at best, and disastrous at worst.
This is true. . . But I am still going to ship characters XDOkay so to answer both your questions...
It would be disastrous because think about it ...
All of a sudden there would be two clans that were joined in the most binding way possible. At that point, there would be an imbalance in the council as they would tend to discuss things together and make a unanimous discision.
What would happen if they had children? What would happen if they had only one?
There are a lot of complications.