What is meant by 'genuine affective' considering a homosexual relationship?

In the Catechism of RCC #2357 is written that homosexuals can't have a true affective sexual relationship: >They do not proceed from a genuine affective and sexual complementarity > > [CCC - 2357](http://www.scborromeo.org/ccc/para/2357.htm) But what is meant by that? I know that it is a sin for them to have sex because there is no sexual complementarity. But why isn't it possible to have genuine affective complementarity? In my understanding affection is often associated with a feeling or type of love. But does RCC says that there can't be love between two persons of the same sex?