Can't get "claim throne to work"

[BunnyThyme]

no matter what happens when i claim the throne of another country nothing results but the loss of prestige.

i have attempted multiple time, the heir has a weak claim. i have more prestige than they do even after the throne is claimed. and there is a royal marriage. i have gone to the declare war tab to see casus belli's and there are none before or after thier new ruler is in power.

[Thrax]

Claim throne works when they have no heir at all and you must not be too small. The casus belli is aviable when you are of the same dynasty ( and he has low legitimity i think)

[Mikey]

Claim throne: If you have a royal marriage with another country and they have a disputed succession (either no heir or an heir with low legitimacy) you can take the diplomatic action to claim their throne. Taking this action will give a -50 relations penalty to all countries you have a royal marriage with, including the -100 penalty with the target.
It makes your monarch the favored successor should their king die without an heir; however if another country has also claimed their throne, and have both the same Dynasty as the target, it will result in a succession war.
The biggest benefit from claiming a throne is that it gives you a claim throne casus belli to force the target country into a personal union for 84% warscore, rather than hoping their king will die without an heir. Since this casus belli always costs 84% warscore, regardless of size, it's one of the best ways to gain large swathes of territory for little cost.

NB: since 1.2 the CB is now only granted when claiming the throne of a country with the same dynasty as yours.

http://www.eu4wiki.com/Personal_Union

[jords321]

claim throne only gets you a PU if there ruler dies, if an heir is born before he does then your out of luck. To get the claim throne CB though you need to be the same dynasty (hover over your rulers name to see)