I have my daughter married my liege. They have a daughter (my granddaughter). I also have a grandson (from a son, who died).
To become a liege (in the next generation) I want to marry them. But when I offer the liege to arrange a betrothal I can't select my grandson. He is not landed, is 8 year old.
I guess I realized the answer: I can only arrange anything (either marriage or betrothal) for somebody who is in my court.. Am I right?