Slitherine

My current ruler is 17 and unmarried. I would like to get him a wife to start producing heirs. How does that work, do I have to arrange marriage through diplomacy or is it handled automatically by the game? I did not see anything in the manual on this.

That is random as far as I can see, but you can try to ask one of your neighbours for a royal marriage, but read the fine print in the manual what the consequences are.
I don't think a Seljuqqie wife is available, maybe the Rus have one?

Unless my ancient brain is failing, at present I think you can only marry off a daughter. A wife for your ruler will pop up randomly, you will see a notification about his taking a wife. I am not sure if other nobles get wives, I don't recall ever seeing any notifications about a non ruler having a marriage. I do believe that they can have a family already when they take the throne.
You can ask for a groom in a trade agreement, but that runs the risk of your territories being given to your wife's father if you don't produce an heir and your ruler expires. I have inherited regions by surprise this way in a few games.

Thanks guys.

We are not CK3 here where you can marry who you want ...

I sent my boy-emperor to war to make a man out of him. They grow up so fast…

So it is automatic. A Wife turned up when my ruler turned 18.

Glad to hear he is no longer a bachelor. Now he can start creating a new horde to carry on the family name.