Eugenics and pedigree are a big aspect of Tevinter. Remember how Dorian mentions that he's the only child and heir of his family, the same with Alexius and Felix. Mage families literally put all their eggs into one basket. They never seem to try have more children, remarry or adopt. Not very smart.
This is so weird to me. This is pretty much every magisterial family we hear about, Maevaris is an only child too, and barring magic sex reassignment, kids aren't happening with her either.
I would hardly base such an assertion on that limited amount of families. We've not heard of the family details of other magisterial families. Those three could be an anomaly, or simply an oversight by the writers. They wanted to focus on Dorian and his issues, so he is an only child. They wanted to focus on Alexius and Felix, so he is an only child. They wanted to focus on Maevaris and her issues, so she is an only child. That doesn't mean that we won't meet other families that have multiple children at some later point.
However, I will say that it could be intentional to some degree to avoid familial infighting. Or there could be fertility issues due to generations of close breeding.
Yeah, nobody important sires heirs in Tevinter, it seems. Or Orlais. Or Nevarra. Or Ferelden.
Very strange, if this is all supposed to be coincidental.
Not accurate about Orlais. Emperor Emperor Judicael II had twin sons. His brother, Florian, had a daughter. All three of these died as a result of the Hundred Days Cough. Judicael II lost interest in ruling and died in a horse accident, leading Florian to succeed him. When Florian died, Celene became empress.
Florian had little interest in his own child, even before she died. He was rumored to have had his cousin (the one who ruled Ferelden) as a lover. If he was actually gay, that might explain the reason for only a single child and the lack of interest in that one, since he likely wasn't interested in producing her in the first place.
I'm not sure if Celene is gay or bi. Her supposed attempt to unite Orlais and Ferelden with Cailan doesn't necessarily speak to her sexuality, but only her ambition. Otherwise, she seems too independent to take a husband and become pregnant.
As far as it all being coincidence, some of it may be simply because it's easier for the narrative.
Also, don't forget the Vael family. Sebastian was the youngest of three.