Originally named Nachman Schachnowitsch1236

The clear statement from the various Courlanders is that Norton and Louis were brothers, with a third brother Janno, and that the original surname was spelt Schachnowitsch.
On Norton's wedding certificate, Jano Courlander is named as his father. In his memorial for naturalisation as a Britsh Subject in 1898, Norton gives his father's name as Styia Schactnowitz and his mother as Fage Schactnowitz. According to Phillip Kirby, the Polish word Styia means 'Uncle of the Bride on her Father's side'.
The Latvian Jewish web-site has references to various Schachnowitzes, including in Goldingen. I am assuming that this is the place of birth that Norton refers to in his memorial for naturalisation (Revision Goldengen is written both there and in Certificate of Naturalisation). In the 1881 census, he appears to give his place of birth in Lapland.
On Louis's wedding certificate, Isaac Courlander is named as father. In his memorial for naturalisation as a British Subject in 1879, Louis makes no mention of names of his parents, but specifies his place of birth as Libau