Historically man boy love was extremely common - e.g. Classical Greece. With the arrival of Christianity, it became far more rare, though never disappeared; there is a tradition of encouraging beards in monasteries to reduce the attractiveness of the younger monks to the older!

When the gay community first emerged as a campaigning group, it was seen as boylove friendly, but at some point chose to seek respectability by trying to construct a strong barrier between adult / adult relationships, and those involving younger people. However the agenda still emerges occasionally, most obviously in the sub-plot of 'Queer as Folk' where the youngster in that is below the Age of Consent when he is seduced / throws himself at one of the adults. (UK version 15, US 17)

Ultimately their 'sexuality' is whatever a person experiences it to be. For us, stuck with an attraction to underage boys that we probably didn't choose, and certainly can't get rid of, it's who we are. To delegitimate that whilst accepting other forms of attraction as legitimate 'sexualities' is, ultimately, a morally driven decision, and not one that is helpful to deepening the understanding of the church for our struggles...