 He was a brother of Niels Ihlen and Wincentz Thurmann Ihlen, an uncle of Christian and Nils Claus Ihlen, and a granduncle of Nils, Joakim and Alf Ihlen.He married Belgian citizen Ambroisine Pauline Rouquet in February 1868 in Our Saviour's Church, and the couple had five children.One daughter, Celina, married landowner and politician Christian Pierre Mathiesen, and was the mother of Haaken C. Mathiesen, Jr. Another daughter, Barbara, married barrister Arthur Knagenhjelm.