Thijs Courtland's full name was Nathan William Courtland, but he was called Matthijs (or more often the nicknames Mates or Thijs), probably after his maternal grandfather Matthijs Verboom.
When Thijs's father emigrated to the United States in 1885 he assumed the surname "Courtland" as his older brother Pieter Spruijt (Capt. William Courtland) had done several years before.
Thijs was one of eight children. His siblings were Pieter Krijn Spruijt, who died in infancy in the Netherlands; Clara Adriana Spruijt (Courtland); Pieter Krijn Spruijt (Carl Peter Courtland); Willemina Martina "Minnie Spruijt (Courtland); Richard "Dick" Courtland; Jennie Courtland; and John H. Courtland.