Cant really believe this happened
So i was with this girl for about 6 months and she decided to get back with her ex boyfriend...i got over it. Now, three months afterwards, ive been talking to a new girl where i work..and we've been getting rather close, flirting all the time, and i would like to ask her on a date. Turns out this girl im talking to now, happens to be the sister of my ex's boyfriend! I didnt realize because of a difference in last names, but they live together with the same parents. Now im pretty sure the dude hates me for "breaking him and his girlfriend up", which i didnt do at all but he supposedly believes, and i dont want my ex to think im trying to stay close to her or anything...any advice on how to handle the situation?
Its not even like i live in a small town...really cant believe this one