I actually gained land by dynastic inheritance in my first game. My Homna son married an eldest daughter of a Uesugi vassal. That vassal dies w/o male issue. My son took over the province, transfering his allegence to Uesegi.
I think it's important to note this son held no Homna titles; had this been the case the inheritance/transfer probably would not have gone through, I'm guessing.
So long story short, my son inherited, but I lost my son (and daughter in law, of course) to the Uesegi clan.
But only temporarily. My older sons died, making this 3rd son the new Homna heir. It was a very odd situation to say the least, having a clan heir who was officially in another clan, but there you have it. Then when my clan leader dies at 71, boom! I got my son back as my new Homna clan leader, and he brought his wife and Uesugi provinces with him.
Yes, provinces plural. The Uesegi to a shine to my son apparantly, and bestowed three additional provinces on him during his tenure there. So, I essentially gained 4 provinces peacefully. Not bad considering Homna island only starts with 3 provinces.
Nice
Yes, inheritance can give you some interesting situations from time to time. For instance, the Ashikaga clan starts with two brothers in a civil war. Should however these characters die, there is a third brother - Masatomo, who is a daimyo under Uesugi - who inherits the Ashikaga clan and takes his province and his two vassals with him when he leaves the Uesugi. I've seen this happen and it's probably the best chance the Ashikaga shogunate have to survive.