OMG...if you knew that person is involved with someone already then its your responsibility to back off....dont ever try to get in or involved yourself with that person.It will be a big problem and you will be hurting each other as will as the person involved with that certain person. if you say your deeply inlove with that person and your having a hard time to forget him/her then. its time for you to use your head? in that case that person is not meant for you, just put that in your mind...you deserve someone better or the best for you. remember you can still love him/her by just making that person happy or untroubled. thats life....(^V^)