WHAT DO I DO

I HAVE KNOW MY BOY-BEST FRIEND FOR ALMOST 12 PLUS YEARS NOW THAT HE HAS A GIRLFRIEND SHE IS TRYING TO KEEP HIM AWAY FROM ME BUT HE WANTS TO BREAK UP WITH HER BECAUSE OF ME , BUT HONESTLY I DONT WANT THEM TO BREAK UP SO WHAT DO I DO TO CONVINCE HIM NOT TO BREAK UP WITH HER?!!!!!