4/10 -- 11:40 AM PT -- Emilio Valli's restraining order was granted... TMZ confirmed. Frankie is protected under the TRO.

5:20 PM PT -- A rep for Frankie Valli tells TMZ ... Frankie is saddened by these unfortunate events and appreciates that his privacy will be respected as he works out these family issues.

Frankie Valli's son is accusing his other son of breaking into their father's home and threatening to harm both of them ... and now, he wants court-ordered protection for both and his famous father.

The singer's 29-year-old son Emilio just filed for a temporary restraining order in Los Angeles against his 36-year-old brother Francesco -- claiming his older sibling attempted to bust into Frankie's property last week ... only to go on and allegedly hurl threats at them.

Per the docs, obtained by TMZ, Emilio claims he and Frankie have been having this issue with Francesco for months -- explaining their dad provides financial support for his boy ... even though Emilio alleges drug abuse against his bro, and says he's gotten desperate lately.

Emilio claims Frankie has recently cut off Francesco ... and that led to him allegedly trying to break into the home on April 5 -- during which Emilio claims Francesco threatened to harm and kill both Emilio and Frankie ... which he says has left their dad fearful for his life.

Emilio goes on to claim in the docs that he believes Francesco is pawning off their dad's stuff in order to score opiates -- and he suggests that might be why he showed up to the house.

In the paperwork, he goes on to say this is an alleged pattern of behavior by Francesco that's getting more erratic ... and they need a judge to step in and grant them a forcefield ... which Emilio is hoping will keep Francesco away from them, and the property.

We've reached out to Frankie for comment ... no word back yet. A judge has yet to rule.