Three half-siblings meet each other for the first time after their absent (and now dead) father left them millions of dollars, with one big catch.

Maybe in order to get it they have to give it away - catch 22 - but they could change lives in the process and maybe change themselves. You could also put a comedy spin on it if all of the siblings were con artists looking to rob each other blind through fake charities etc...I sense you already have the plot though, maybe you just need to work on the log line as suggested above.

Three more movies about inheritances that come with a catch:

Dawg: To inherit a million dollars, an egotistical man must find all the women he's betrayed and convince them to forgive him.

The Ultimate Gift: When his grandfather dies, his grandson must perform a series of tasks to get the inheritance.

Scavenger Hunt: Relatives must engage in a Scavenger Hunt to determine who will get the inheritance.

So, what Richiev said. There's nothing novel in a story about an inheritance that comes with a catch. The hook is the nature of the catch; it has to be part of the logline.

Three more movies about inheritances that come with a catch:

Dawg: To inherit a million dollars, an egotistical man must find all the women he's betrayed and convince them to forgive him.

The Ultimate Gift: When his grandfather dies, his grandson must perform a series of tasks to get the inheritance.

Scavenger Hunt: Relatives must engage in a Scavenger Hunt to determine who will get the inheritance.

So, what Richiev said. There's nothing novel in a story about an inheritance that comes with a catch. The hook is the nature of the catch; it has to be part of the logline.