He's supposed to be. He was born at Prague in 2007 and came to Chester in 2009 as a breeding male although as you say he doesn't look like a typical Sumatran (white "mane" around face, he's relativly small compared to a a pure Amur individual, and more stripes than you can count!) when I first saw him in the flesh I was also taken aback by how similar he appeared to an Amur youngster.
Just before this spins off into speculation - as far as I'm aware there has never been any suggestion that 'Fabi' is anything other than pure Sumatran.
