Steve Aoki -- FINALLY Getting Benihana Money ... But There's a Catch

Famed DJ Steve Aoki's wallet is about to get fatter -- cause after years of legal battles he's finally defeated his stepmom for control of his late father's Benihana fortune.

Steve and his sister, model Devon Aoki, were each awarded 50% of their dad's trust by a judge this week ... meaning they get ownership rights to Benihana and a chunk of restaurant income.

But they don't get it just yet ... according to the Aoki family lawyer neither gets paid until their 45th birthdays. Steve is 36 and Devon is 31.

Benihana founder Rocky Aoki married Keiko Ono Aoki in 2002, and his kids feared she'd cut them off when he died -- so Rocky amended his will to give his descendants sole control of his trust.

Keiko's been challenging the will ever since Rocky died in 2008 -- and actually won in a lower court. This week's ruling overturned her victory.