The age at which a person's family and friends, and indeed society as a whole, begins to seriously suspect he/she is gay. Generally at least 26 or 27, a person at the Age of Suspicion has never had a long-term boy/girlfriend, nor wife/husband (which would exonerate him/her from suspicion). With the Age of Suspicion, homosexuality is not necessarily viewed as undesirable or wrong, it more marks the time when a person's family and friends are fed up with him/her being "in the closet," if he/she is in fact gay.
"Patrick is turning 30 this year.. no wedding in sight either"
"He's approaching the Age of Suspicion. Someone should tell his parents"