Is it wrong? To talk to his bestfriend?

I dated this guy James for awhile nd he had a best friend blaster who I thought was Alright but I never talked to him well James left me for his baby mama nd somehow me nd blaster started talking now were messing round acting like a couple is it wrong of me to me messing with blaster if that James best friend? I'm still cool with James as for blaster I really like him help!