Simplify the following text for a Grade 7 native English-speaking person.
Original: Michael Spinks ( born July 13 , 1956 in St. Louis , Missouri ) is a retired American boxer . Nicknamed Jinx , which spawned the nickname of his right hand : The Spinks Jinx , he is the brother of former heavyweight champion Leon Spinks , and uncle of Cory Spinks , a former welterweight and IBF Light middleweight champion .
Simplified: Michael Spinks is the brother of heavyweight champion Leon Spinks .