Not Only Will We Complete Each Other's Sentances...

....we are going to look alike, too? Depending on your spouse's looks, that could be good news or bad news. The study here.

Genetic influences are also a factor. A past study showed that genetically similar people have better marriages [Source: Live Science]. Such families have fewer incidents of child abuse and a lower rate of miscarriages. People also appear to be more selfless when involved with genetically similar partners.

So the key is to be similar but not too similar, if you know what I mean.

Of course, couples shouldn't be too genetically similar -- in most cultures, relationships between close relatives are taboo, and geneticists agree that diversity is important to a healthy gene pool.

Besides feeling that they work better together, why and how do people choose partners who are genetically similar? Asking for a DNA sample on the first date would be impolite. The answer may be equal parts personality -- derived in part from genetics and consistently ranked by people as important in a partner -- and the marriage models we have around us. In other words, many women say they want a guy like dad.

Well, some do. And some run away and try to find the exact opposite.