He was the son of Andrew McElvaine JP and Susan McElvaine. In 1901 the family lived in house 14, Lisnabrague, Scarva, Co. Down. By 1911 the property was known as house 7, Lisnabraque, Scarva, Co. Down.
The family also lived at Union Lodge, Poyntzpass.
McElvaine served with the 18th Bn. Tank Corps and attained the rank of Lieutenant.
The Belfast News Letter of 17th May 1917 reports:
The Belfast Banking Company 'Roll of Honour' booklet records McElvaine as 'previously wounded'.