I've never heard that Nick Carter was/is LDS (Mormon), nor can I find anything to substantiate it. Though it seems one answerer (Ray Ray) might actually know the truth (whether or not you can trust that is another issue). But I do have this opinion to give...
While it is disappointing that the label of famous seems to be synonymous with "judicable" in the eyes of society, the only reason I personally, could possibly care how he acts is when he has violated a secular law. Otherwise, I have to agree that with whom or what group he associates, and his orientation or behavior is between himself and the Lord, and/or his religious leader (if he has one). He has only to himself and the Lord to answer, no one else. And really, we shouldn't be classifying him as anything, except from what he has told us he is, and we should respect (not judge) him despite whatever that may be or how he acts.
Second, the idea that homosexuals cannot be or become LDS (Mormon) is completely false if not somewhat a disgusting assertion. Granted, in order to receive certain privileges within the religion, one must obey certain commandments, such as the law of chastity or marriage (as defined between a man and woman only). But simply being homosexual does not preclude you from receiving ordinances or blessings; it is entirely based upon what a person *does.* And in any case, such things are none of our concern. While our actions might individually define us and our level of activity/privilege, it does not determine for us with what we will choose to associate religiously/philosophically, and should not be a source for disrespect or unrighteous judgment. Anyone can become LDS, and we welcome people of all types.