William John McMillen was born at Rotterdam Street in Belfast, Ireland on 13 April 1876. Raised in a Church of Ireland family and one of eleven children, he was the son of Thomas McMillen, a marine fireman, and Maria Croskery. 

Described as a seaman, McMillen was married in Belfast’s Trinity Church on 13 May 1902 to Sarah Jane English (b. 20 July 1877), herself the daughter of a seaman. They had four children: Myrtle (b. 1902), William (b. 1905), Maggie (b. 1907) and Lizzie (b. 1910) and the 1911 census shows the family living at 13 Shipbuoy Street in Belfast.¹ Four more children would follow: Robert in March 1912; twins Maria and Sarah in June 1914 and Richard in September 1916.

McMillen’s ship prior to Titanic had been the Duke of Connaught. He joined Titanic at Belfast for the delivery trip to Southampton where he then disembarked. Also serving aboard Titanic for the delivery trip was his younger brother Samuel McMillen. 

William McMillen remained at sea in the following years and served with the merchant fleet throughout WWI and after, continuing to make Belfast his home. Widowed in April 1930, William died at his home at 80 Turin Street on 31 December 1956 aged 80. He is buried in City Cemetery, Belfast (plot D1 122).