In twilight is Edward the youngest?

Technically, yes. Both he and Jasper were changed when they were seventeen, but acknologing their d.o.b's, from oldest to youngest it goes something like this; Carlisle, Jasper, Esme, Edward/Alice (both born in 1901-ish) and last but not least, Emmet/Rosalie (both born in 1915). Of course, if you include Bella, she would be last as her d.o.b is 1987. Hope this answer is okay=)