My best mate almost had an affair with my sis in high school & now moving closeby us yrs later, how do I handle it?

Me and my best mate were pretty close in senior high, but he changed a bit, turned out to be a big jock type, smooth talking and went on moving on from one girl to the other, used to flirt up our teachers, who would respond in Kind and was having many gfs.He was like 6.4 , not bad looking and had noo issues chatting women up, while I on the other hand was a one girl type, crushed on one girl all throught and never acted on it.It was like suddenly he outgrew me and I was kindoff feeling resentful about it.He was also not an open guy, had his own private life, once he had an affair with his neighbour(who was like 23 or 24 then or older to us) and she got knocked up(rumor is/not confirmed but people say), so there were some issues and he dint come to write exams for like 6 months.When he returned, i asked him, what had happen and he wasnt willing to share.

Being a close friend of mine hed often come home, to browse or play station and sometimes when i go to meet my sis during breaks at where we were studying, hed materialize out of nowhere and started to tag along.Overtime, my sis got used to him being around. One odd day out of the blue, he asked her “sis can you see me as your own brother” and she kindoff was confused for a second but told him “hey your my own brother” and then looked at me in a sort of guilty way!.Now about sis, shes long legged, above avg stature and likes heels, likes to look big and I was an avg guy, shes actually joked that im kindoff small compared to her and so when she said hes her brother, i started feeling perhaps because she feels protected by a much larger, more imposing guy and I went red and couldnt understand the melodrama of him wanting to be her brother.It was like suddenly my close mate became family!!.So now, it was as if she had two older brothers and we often spent time together both in School and at our home. One day it soo happen I spent some additional time on the net and when I walked in to the tv room, saw him sitting close by her on the couch both watching tv and he had her hand on her shoulder(like tapping on her bra strap) and she was in her home nighties.I went red,I felt jealous and angry and I walked in, but he dint take that hand and I started fuming, but dint make a scene. Anyways, we moved out quickly and he became an Orkut friend and then a facebook friend! and we both stayed in touch nominally and my sis also on his fb.

Sis got married and she lives close by me and then our old friend messages me and says hes moving close by and that he wants our old friendship and family!(implying us).Since we have been close growing up, I told my sis that hes coming and what I should do?Shes like , hes ur friend right?you should help him settle down!.He asked how she was?I said, shes fine and told her he asked, she was like, what did he ask?I said, nothing just how you are and that hes looking forward to old time friendships with us.She was like..Ok!.

So, now, I have this close friend whose been close to us, but I,m skeptical of him since those days, i,m confused whether to keep in touch and be friends like old times or no