
Well technically, the king is able to not have kids if they want to but the future king would be a relative.
Kings usually have children so their future bloodline could rule the country but if they don't want their future bloodline to rule the country they can just not have kids and let a relative to rule the country
Since people are power hungry kings would rather let their child be the ruler.
Shin is forcing Wolfgang to have a kid so they he can rule the country stronger so no one can oppose him. And since they sacrificed so much to make Wolfgang king, it'll be a waste for him to not kids of his own

Like you said, kings can do whatever they want, and they don't have to have kids. has for hair's it's fine, the old king have enough basters sons like the sea so I don't think they really need to look far at all. there is always be a lot of bloodlines since he had a lot of sons.
and let me tell you, even if Wolf will have son it won't make him the best king/hair in the first place. blood does not rule anything in those cases, Wolf can have the worse son to be king or hair so they would have to search someone else anyway ╮( ̄▽ ̄)╭
so what is the point in forcing someone to have kids in this case? again. Shin is being an idiot moron and does not see the whole picture or Wolf feelings.
I feel bad for Wolf but he choose him so he will suffer I guess

I mean yes he can not have kids and find another heir but Shin knows if he has his own people will look to him as more of a ruler. It's just part of royal psychology. I agree with Shin being silly but I cannot be harsh on him. I know everything he does is for Wolfgang. Although Wolfgang time and time again says he cares not about those things and only about Shin. We will have to wait and see what happens. I mean a lot of people know Wolfgang has feelings for Shin and although Shin does not openly admit it, he loves Wolfgang too.

even if he says it is for "Wolf sake" forcing someone to have kids just cause it "look good as a king" so mostly the kid is just for decoration is still wrong! it's not for his sake at all if you need to force him to have kids with women he does not want! it actually a disgusting point of view he has there ╮( ̄▽ ̄)╭
but hi Wolf choose him so I can't say much
All I want is to see Shin Soohyuk happy (/TДT)/ with Wolfgang of course but I know he is thinking about preserving the line and for Wolfgang to have kids. BUT ALL HE WANTS IS YOU SHIN!!!!!