Since your father is now deceased, there is no way to contest/change the bene he named on the policy. He would have had to change the bene himself while living. It happens fairly often that people do not change the bene(s) on their pol. & the person(s) they really want to have the benefits are left out. Be happy the ex is willing to give the pol. proceeds to you & your sister - many would not.
Too often we underestimate the power of a touch, a smile, a kind word, a listening ear, an honest compliment, or the smallest act of caring, all of which have the potential to turn a life around. Leo Buscaglia
Live in peace with animals. Animals bring love to our hearts and warmth to our souls.