I have heard another account, though similar to your own:
Fr. Valentius (Valentine) was a priest who secretly wedded couples together during emperor Claudius’ ban on marriages in order to encourage more army recruits. The emperor found out about the father’s secret weddings, captured him, and tried to persuade him to convert to paganism. When Valentine refused, and even tried to convert the emperor, Claudius had him stoned and beheaded. During the days that St. Valentine was imprisoned, he wrote a letter to the blind daughter of the jailer and signed the farewell “From your Valentine”.
Has anyone else heard this rendition of the story?