Mr Nikolai Johannes Peltomäki was born in Lavia, Finland on 26 December 1886; he was the son of Oskari Juhonpoika (Johansson) Peltomäki, a general labourer/crofter, (b. b. 3 February 1855 at Lavia-1924) and Josefiina Taavetintytär (b. 19 October 1851 at Lava, d.1931). There is a chance his parents had married 27 November 1877.

His brothers and sisters were Hilma Aurora, b. 2 January 1873, Wilhelm Fredrik, b. 13 July 1877, Aina Sofia, b. 2 December 1879, Frans Oskar, b. 17 June 1882, Anshelm Ewert, b. 28 September 1884, Eino Otto Arvid, b. 30 January 1889, Fanny Matilda, b. 21 March 1891 (d. 6 November 1891), Martta Johanna, b. 1 November 1892, and Laina Eliina, b. 21 January 1898. His two eldest siblings were apparently born out of wedlock.

Nikolai is understood to have spent time working or studying in Pori in western Finland from 1902; he later ended up working in Tampere but by 1906 he had moved to Helsinki and was working as a painter and as a shop assistant in a bookstore. 

Peltomäki, who was unmarried, boarded the Titanic at Southampton as a third class passenger (ticket number 3101291 which cost £7, 18s, 6d) and was described as a general labourer; he was destined for New York City.; the reason for his travelling is unknown. 

Nikolai Peltomäki died in the sinking and his body, if recovered, was never identified. 

His father died in 1924 and his mother in 1931.