Emigating under false name?

I believe my grt grt grandfather Andreas Syversen Skartlien, b. 1835 in Torpa in Oppland came to America around the year 1866. I have not been able to find him on any passenger lists, however I just did find his brother Marthinus, two years younger than he, on an arrivals list at Quebec for the ship ANNA DELIUS in June, 1866. Going back and checking the Emigrants 1825-1875 passenger lists here I found him listed as Marthinus Skortlien. So he was in Quebec in June 1866. The trouble is, he was listed at a baptism for a son(Sigvart) of his brother Nils Syversen Skartlien in July 1866, and then he was married in April 1867 at Aamot church in Torpa, Oppland. Is it possible that my Andreas could have emigrated to America under his brother Marthinus' name? If so, why? Was he maybe escaping the military service or what?