Wrong Box, The (1966, U.K.)

John Mills, Ralph Richardson, Michael Caine, Peter Cook, Dudley Moore and Peter Sellers star in this delicious black comedy.

A family in Victorian England learns that a large inheritance will go to the last surviving family member.  This sparks a dangerous contest between the elderly brothers as they fight to be the last man standing.  Then things get really wild when their families desperately join in to get their hands on the family fortune!