Sexual issues are the hardest to deal with. Wrapped in problems of intimacy, of love, of acceptance, of union, and fuelled by hormones, by psychology, by biological clocks, by the bombardment of erotic imagery, by peer pressure, sex destroys more than it creates or so it seems at times.
I advocate a pastoral stance regarding friends and family caught in such dilemmas. Firm on your beliefs, but loving. Loving the sinner but hating the sin is the thought that comes to mind.
A danger exists: you have to be strong in your principles. You cannot allow them to be compromised when they are assaulted, and they will be.