probably by Jacopo de' Barbari. The other guy is potentially Durer. He also looks similar to the Man in Leonardo's "The Musician" - there is something weird about him!

Luca Pacioli

Paccioli, Paciolo or Luca di Borgo - 1445-1517 wrote: De Divina Poroportione which Leonardo illustrated. The only thing Leonardo did that was published in his life time.  He lived with and taught Leonardo mathematics around 1497-1506.

See De Divina here: