St. Nicholas. And even then, most of the legends are talking about the same person.
Sidenote--isn't it interesting how the saints who have the most mainstream appeal and recognization are also the ones whose stories are so muddled? It's like a strange and unfortunate game of theological telephone. We'll see what I come up with for St. Patrick (spoiler alert: nothing to do with snakes).
Here's what we do know--Valentine was a Roman priest who was beheaded on February 14, 269. He is recorded in St. Gregory's sacramentary of martyrs and other martyrologies.
That's about it.
He is the Patron Saint of bee keepers, engaged couples, epilepsy, plague, and travelers.
How Valentine's festival day became associated with love and romance is one of those weird, convoluted histories which you can never be quite sure of. Some sources say that he was an extraordinary lover of God and people, but honestly I don't expect anything less from a priest--especially a saint. Additionally, it seems there was a pagan ritual held in mid-February that included drawing of names and goddess worship having to do with Juno Februata. But even that is an uncertain legend and a tenuous link. Chaucer also had something to do with conflating St. Valentine and courtly love in Parlement of Foules, but it's unclear what led him to make that connection.
All this to say, this is another saint-related holiday in which the actual saint has hardly any relevance.
Happy Valentine's Day!