Evgeny Sveshnikov, born in Cheliabinsk, Russia, on February 11, 1950, is perhaps best known for the opening named after him, the Sveshnikov Variation of the Sicilian Defence (1.e4 c5 2.Nf3 Nc6 3. d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5). To be honest, having played the Sveshnikov Variation many times before, I hadn't realised this grandmaster was so young! Evgeny Sveshnikov became an IM at 25 and a GM at 27.
It is interesting to note that in January of 1984, Sveshnikov was diagnosed with third stage cancer. He survived and went on to live a normal life.
Check out ChessBase's tribute article "Evgeny Sveshnikov turns sixty".