I found one bug when playing with the Kingdom of Asturias.
There are many factions that are same people as you (when playing as Asturias, for e.g. Pamplona, Gascony, Provence...), so in diplomacy there is an icon, like shaking hands, that says we are the same people/blood and we can ask that faction to join our side (our kingdom). We had that same option in R2TW, e.g. when playing with british tribes.
But now when you enter diplomacy with the country that has same people as you, there is no option to ask them to join you side.
Hope they fix it soon.