Is it true that a man or woman could have homosexual relations earlier in life but then become completely straight later on? Anon.
No. What is more likely is that the individual can't deal with his or her homosexual feelings and goes into the closet. They may lead a heterosexual life including marriage (to a member of the opposite sex) and children, but homosexuality is not a phase or something that just goes away. It is often said that youth is a time of experimentation, and that a person may fool around with members of their own sex before realizing they prefer the opposite sex. The trouble with this theory in almost all cases is that there is no corresponding push for people to engage in homosexual relationships the way there is with heterosexual relationships; as well, people tend to repress their homosexual tendencies, not the other way around. It's more likely that as the individual gets older they worry more about society's, as well as their friends and family's, reaction to their sexual orientation -- many people have a more devil-may-care attitude toward their sexuality (and everything else) in their youth that fades away as they face the reality of what openly facing the world as a gay person might mean. Even today there are people who are closeted and/or in denial in regards to their sexuality, people who strongly desire (and may regularly seek out) members of their own sex but who insist to themselves and others that they are straight.
The key is not to "reassure" these people that they are straight but to convince them through counseling that "gay is good" and they, too, can lead happy, healthy lives of self-acceptance along with those of us who are Out and Proud.