Quote Originally Posted by HoreTore
Not sure about tweaking it, but you can control it. Don't accept ANY offers of adoption to your heir, and don't marry his daughters. Wait until a male son has come of age, and the old king dies. Then you are free to accept marriages and adoptions, as the son has been named heir.

What the problem is, is that the heir is designated at the moment the old king dies and the new heir MUST be of age to consider. The oldest son of the new king will be chosen, or the adopted son of his oldest daughter...
Indeed, but wouldn't it be harmful to reject all suitors, since one would have considerably less generals?