5:50 PM PT -- Ricky Martin's attorney, Marty Singer, tells TMZ ... "Unfortunately, the person who made this claim is struggling with deep mental health challenges. Ricky Martin has, of course, never been - and would never be - involved in any kind of sexual or romantic relationship with his nephew."
Rick's rep adds ... "The idea is not only untrue, it is disgusting. We all hope that this man gets the help he so urgently needs. But, most of all, we look forward to this awful case being dismissed as soon as a judge gets to look at the facts."
4:05 PM PT -- Ricky was spotted on the set of "Mrs. American Pie" Friday in Los Angeles.
Ricky Martin's alleged domestic violence accuser is one of his own family members ... and now the pop star's reportedly staring down the possibility of a half-century behind bars.
A new report Friday from Spanish news website Marca identifies Ricky's accuser as his 21-year-old nephew, Dennis Yadiel Sanchez, which would introduce incest into the case in Puerto Rico.
The singer's brother, Eric Martin, reportedly identified the alleged victim ... and Ricky is going to court July 21. Under Puerto Rican law, there are harsher penalties for certain sexual crimes when the alleged victim is related to the accused, but it is unclear exactly what Martin is facing.
Nevertheless, Marca is reporting that Martin faces up to 50 years behind bars if convicted.
As we reported ... Ricky was accused of domestic violence earlier this month, and the alleged victim, whose identity was previously unknown, got a temporary restraining order against Ricky, who has denied the allegations.