Why did Sadeas never....
Rhythm of war spoiler tag since Amaram Sadeas thingy
But why did Sadeas never have kids?
Gavilar had 2, Dalinar had 2, Ehlokhar had 1. If Adolin had been able to hold a relationship long enough he might have had a kid by the time of Stormlight 1
Sadeas wasn't stupid, he had to have known that eventually he will die and his HighPrincedom would need an heir to succeed him.
Sadeas had that curvaceous woman, they were as in love as one could expect of them I think.
Even if Sadeas couldn't produce biological heirs, he would certainly have an heir named of one of his vassals
The Amaram thing seems to come out of left-field in my opinion. And the Amaram thing could still be done if Sadeas had kids too young to assume the duties of high prince