If I have Gavelkind and my Character has two Duchies and several sons will each Duchy be inherited by a different son with remaining sons becoming count vassals?
Yes, Gavelkind splits up the realm on succession.
The Duke that's imprisoning her is showing as her heir, though. I'll try ransoming again later.
If they are rivals he probably won't ever ransom her, FYI.
Thank you, I think I'll take the prestige hit to protect my heir, expanding both kingdoms at once (My son is fighting to claim part of Wales to go with the entire South he runs) and I plan to take Mercia (having already taken Hwicce, both being England's two strongest Duchies)
Why break the truce? Can you raid them? If so, do that instead. You turn hostile to their troops when you raid them, so you can wipe out their armies while your son actually sieges down holdings for war score. It's a tactic I like to use a lot to screw with the Umayyads in the early starts.
Anyways a new question I had was I know Merchant Republics have limited crown authority, but could you get imperial administration as a merchant republic/before swapping to Merchant Republic?
You can't have Imperial Admin before changing to a MR, because you can't change from Feudal to Republican (without mods, I think the exploits/bugs have been squashed?). If you can get the ERE as your primary you should get Imperial Admin though, but other threads have said it's not working lately, so I'm not sure.
Something else I was thinking was that since you are stuck with low crown authority as a Merchant Republic, do your vassals declare wars? I was planning on having republics as most of my head vassals and I have heard they are rather passive in declaring wars or forging claims (I presume due to the fact that some random bloke takes their place after they die) is it just so the five patrician families can fight with eachother or can the other famlies fight for land in and out of the realm?
Your vassals will still war, and I think regular republics will stay more pacifist yes. I haven't run with them because I play with the rule limiting them, and I usually play as Feudal. Without higher Crown Authority (I take it you don't have Conclave?), you can't stop vassals from fighting internal or external wars. That's one of the major trade offs Merchant Republics have.