yes, the previous generation, my friends father married to his mothers sister
the legal agreement is considerd only when the first is impotent or cannot have children ( this is the reason in most of the cases) its almost like a divorce to the first one
Dharmendra Film Actor, converted to muslim on records just to marry hema malini, he changed his name to dilwar khan
http://www.milligazette.com/Archives/2004/16-30Jun04-Print-Edition/163006200433.htm
but they never follow islam