How can i get my freeloader brother to pay back my mother the money he has borrowed?

$6000 court costs fines, Lawyer, $2000 on her Home depot card, and the rest is miscelaneous.My asked him for a measly 150 a month and she hasnt seen a dime in 4 years, my relationship with him has deterioted over this and now hes freeloading off his girlfriend that was in the military and got injured in Iraq.When is he gonna grow up and pay up.What should i do stay out of it, my mom had a stroke 2 years ago and she needs her money.Im the oldest sibling and im looking out for mom that raised 3 kids on her own. Hes 34 and he needs too pay up.