Have you ever had the experience of meeting a stranger who looks familiar, but you just can’t place? Meet the subject of a portrait by Renaissance painter Sandro Botticelli - "Young Man Holding a Roundel" - which goes on the auction block at Sotheby’s in January for $80 million.

Don’t I know you from somewhere?

That nagging where-have-I-seen-you-before question doesn’t pop up with other portrait paintings I can think of, say, Mona Lisa. Mona looks like herself. But the oddly familiar face in the Botticelli portrait was a puzzle until I remembered where I’d seen him before - the woman in Botticelli’s painting "Birth of Venus." The Roman goddess and the “young man” share the same wistful look in the eyes, the same air of purity, and a similar kind of sadness.

What's bothering you?

Venus might be sad because, as the mythological story goes, she knows that her birth is only a dream. Who knows why the “young man,” painted just a few years before Botticelli painted his vision of Venus, appears mournful? Regardless, the two could be siblings – fraternal twins, maybe.

Her lips are sealed

Of course, seeing similar facial features in portraits of others by the same painter is not unheard of. You’ll find Mona’s guise in Da Vinci’s images of other women he pained - the Madonna and Child with St. Anne, and Lady with Ermine. According to art historian Willem Van Loon, in his Book, "The Arts," Mona’s filament-like lips are submerged in shadow because Da Vinci was bad at painting mouths.

You can see the same indistinct mouths in his other paintings of women. And not just the mouths, but also features, such as heavily lidded eyes and pointy chin.

Keeping a secret

The Botticelli portrait, regularly seen in museum shows, is deemed rare, by Sotheby’s, because it rarely gets put up for auction. The auction house hasn’t said who is selling the work and, unless the buyer is a museum, it’s likely the new owner will be a secret, too.

Also unknown is the identity of the young man in the painting. Art News says that it’s Giovanni di Pierfrancesco de’ Medici, brother to Lorenzo the Magnificent, who was a big patron of Botticelli.

Wishful thinking

The L.A. Times, noting that the projected price tag of $80 is expected to go much higher, pointed out that a Monet painting (“Meules”) went for $110 million only two years ago.

The Uffizi in Florence owns Botticelli’s "Birth of Venus," and it would be instructive to museum visitors if the treasure house could buy the portrait, too. That way, art lovers could see the resemblance between the two.

Note: I’ve chosen to picture just the young man’s face and not the roundel because another artist, Bartolommeo Bulgarini, painted the circular disc, which bears the image of a saint.