Makes sense though. Fergus already had an heir and was married quite happily. No reason to rock the boat.
Yeah, I sort of understand that...
Just strikes me as slightly at odds with how the rest of Ferelden nobility is presented in the lore, and especially the idea that nobles are jockeying for power. Even the younger son or daughter of the country's second Teyrn would have to be pretty attractive material for a political marriage, and I doubt Highever would want the opportunity for more power or status to be squandered. Every noble child is useful in that respect, and it seems anachronistic that they'd be willing to let a gay/lesbian offspring get away with not marrying anybody.
(The Noble's mother even mentions marriage in the meeting with that other lady.)