Toni Braxton's Sister -- I'm Divorcing My Cheating Husband

"Braxton Family Values" star Trina Braxton can't un-break her marriage ... the reality star finally pulled the trigger on her divorce from philandering husband Grabriel Adrian-Solis, TMZ has learned.

Toni Braxton's sister filed divorce docs in Georgia court claiming her marriage was irretrievably broken. Trina and Gabriel tied the knot in August 2003, separated in March 2013, and are currently living in separate pads.

It's not exactly a shock -- the duo suffered from a slew of marital problems, including infidelity. Gabriel has admitted to cheating on Trina with numerous women in the past and Trina admitted to cheating on Gabriel -- all of which played out on their reality TV show.

As for the nuts and bolts of it all ... Trina says she'll try to work out a financial agreement with her estranged husband to divvy up their assets (and debts) as calmly as possible. She's asking for a total divorce, claiming there's no hope for reconciliation.

In times like these, at least she's got Toni ...