A lady was dating a guy for two years, the guy cheated on her by sleeping with her friend. As a result they broke up. A year latter this guy and younger sister of the lady started dating unknown to the guy that is ex girl friend younger sister. After dating for  a year, the guy went for introduction for marriage , only for the elder sister to find out it is the guy that she dated.

What would you do if you're this guy or this lady(ex girl friend)?

The younger sister no nothing about this previous relationship with her elder sister even up to now.

This is small world. I will move on with my wife to be, there is nothing else I think could be done, because I didn't know she is the younger sister of my ex. The whole plan Isn't intentional.

Well as a guy I will move with my new wife, but think is ok for the former lady to tell her younger sister what had happened, so that she doesn't hear it some where else.

I think if I'm the lady I will tell my younger sister everything I know, as is better she hears it from me than outsider.

Gloria I agree with you, the right thing to do is to tell her younger sister about whole thing.

The best thing is to becareful. The lady should be careful how she handles this that she doesn't negate her younger sister's family happiness.

A lot of funny things happen in people's day to day life, this ensure requires some kind of wisdom to avoid it being misinterpreted and lead to damage of the new couple's marriage.