I think the thing to do if he's in love with somebody else is to break up with his current girlfriend. But I don't think it would be nice to court the sister. He should stay away at least for a while. If he still loves her after some time, I guess he can but I think the sister wouldn't be so receptive of the idea.

That is a big no-no...its not fair to his gf or the sister and blood is thicker than water just becuase he may have feelings for her sister she may not choose to cross that fine line and date him...so he should stop thinking about it and if he is not happy he should break up with her and move on to another girl.

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"Beauty is in the eyes of the beholder"

I think I agree with zemrat. You will only cause sisters to have a gap. The thing to do I guess is to break up with his current girlfriend if he's not happy with her but he must forget about the sister.

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And they make auctions fun, too.

OMG! what a story. How about the girlfriend's sist? Does she love that guy too? Whichever way, the guy will end up hurting both sisters's feeling. And even make them fight between them. Is the guy sure that its not love but rather a mere infatuation?

The guy should be sure about his feelings.He should know that the mere fact of breaking up with one sister for another one could bring out chaos in the relationship between the two sisters.
It is preferable to break with his girlfriend and find another girl.

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