Lyle Menendez and his wife, Rebecca Sneed, quietly ended their marriage after more than 21 years together, but she remains a key figure in his life despite rumors of a cheating scandal Sneed says are baseless, PEOPLE has learned.

Lyle Menendez, a focus of "Monsters" season two, was first married to Anna Eriksson. They divorced and he later married Rebecca Sneed.

The couple tied the knot in 2003 while Menendez was serving time for the 1989 murders of his and his brother Erik's parents.