Dramamine and benadryl?

hey since Dramamine and benadryl are so closely related does that mean if you build up tolerance towards lets say benadryl, have you also grown a tolerance towards dramamine? I know they are for different purposes but i use benadryl to sleep but i use it often and now built up a tolerance, so if i were to take dramamine for the sedative effects would it work good or do i also have a tolerance to Dramamine now?