How can I convince my brother to break up with his girlfriend?

He is nineteen, and she will be turning seventeen this June. She lies, manipulates, and hangs all over guys at our school. She has personally offended both my sister and me, and he deserves so much better than her. Nobody in our family likes her except for him- she has not one redeemable quality. How can I get rid of her?How can I convince my brother to break up with his girlfriend?
try to introduce him to other women that are older and a better match for him. he needs to find someone his age a couple years older. your family needs to openly and often let him know they dont like her so he can know that it effects the family and he shouldnt be with someone that noboy approves of. Just ask him stuff like ';what do you see in her? do u really want to be with someone approves of'; tell him the things she says or does that are bad. or just let him find out for himself, make him go to parties or whatever that will let him see there are way better girls and that hes out her leagueHow can I convince my brother to break up with his girlfriend?
Maybe invite her over to dinner with your family and maybe this way your brother will see what she's really like.