I'm the petty king of Munster. I have a daughter by my ex-wife and my new wife isn't very fertile. I gave a courtier a good tumble, she gave me a son, and I legitimised him.
I was expecting the legitimate bastard to then become the heir - however, my daughter is still the heir. I'd really like to make my son the heir, to get rid of the "female heir" negative opinion from my vassals. Why did this happen?
N.B. - My son is considered "my son", he is of my dynasty.