Erik Menendez, 54, is in the hospital and has been diagnosed with a serious medical condition, his family confirmed to ABC News.

Erik Menendez and his brother, Lyle, have spent more than 35 years prison for killings their parents in 1989 in a case that over the past year has gained renewed public attention following the release of Netflix's "Monsters: The Lyle and Erik Menendez Story" and various documentaries.

An attorney for the Menendez brothers, who were convicted in the infamous 1989 murders of their parents, says Erik is suffering from a "serious" medical condition and should be released from prison immediately.