Succession Help?

[Meleya]

I have a decent grasp on most of the game's mechanics but I still don't really understand succession entirely. playing as the empire of italy and twice I've had lands that I owned and wanted go to relatives as vassals. just wondering how can I stop this from happening? sucks when you develop land just to have it to to a vassal and they're left making more money than you do

 

[Meleya]

if you try to claim their title and declare war on them half of the country rises up against you without warning? I don't understand

 

[fodazd]

As long as you are on partition succession, your land will get divided among your children. In the succession tab of your realm view you can see the expected title distribution. There are a few ways to prevent this:
-> Find some way to disinherit your non-primary heirs. This can be through the disinherit interaction (which costs renown), by sending them to a monastery or holy order, or by just finding some way to kill them off before succession. In some cultures you can also just castrate them.
-> Give each of your non-primary heirs enough land so that they no longer get anything from partition. This usually requires you to expand pretty fast.
-> Give elective succession to the titles you want to keep, and make sure your primary heir wins the election.

Also, don't tyrannically revoke titles unless you absolutely have no other choice. A lot of other vassals will rebel together with the target.

 

[pengoyo]

Also, don't tyrannically revoke titles unless you absolutely have no other choice. A lot of other vassals will rebel together with the target.

To add to this, you can see if other vassals will join in rebellion by, when revoking a title, looking at the 'on decline' tab and seeing if any other vassals are listed there.

 

[Greifental]

if you try to claim their title and declare war on them half of the country rises up against you without warning? I don't understand

You can try to claim the title. Tell your Bishop/Realm Priest to forge a claim on their counties. If you have such a claim you can revoke without tyranny.

As the others said revoking titles without a claim (or another reason like criminal behaviour - female adulterers in a catholic realm are very good for this, so are any excommunicated characters) is very risky.