Is it possible to have too much in common with someone?

Maybe: Having a lot in common can be great, because you understand each other. But if the 2 of you are always together, your relationships with other people can deteriorate. You might stop doing the things you used to enjoy, simply because your partner isn’t in on it. This can make one feel smothered and irritated. It's healthy for each partner to have his own interests - it keeps things interesting.

Too much incom?: Yes, if u love someone u only look at positive aspect in what he or she does and u turn a blind eye on the negative issues.