Is sex important to a relationship?

I would say yes, sex and sexual issue are very important. Crucial even. If sex was unimportant then cheating would also be considered unimportant. After sex, both partners' brains release chemicals that make then feel happy and most importantly connected and in love. Regular sex bonds a couple together. Needless to say this is far from the only thing bonding a couple. Any physical affection, cuddling, kisses, hugs, holding hands can have this effect as well as the connection from the shared experiences, conversations, similar interests etc. Sex will not always make or break a relationship but a terrible sex life (absent, violent, whatever) or a cheating partner can break a relationship. Sex is more important to some people than others. Some people prefer frequent sex, some people are once a week or even less often. These differences can cause problems. The key is compromise, sometimes you will be having sex that you aren't fully in the mood for, sometimes you will want and go without, as long as one of you isn't always giving way to the needs of the other you can work it out. Sex isn't all there is to a great relationship but it is an important part.