The Duncan family may (as the name suggests) have had some roots in Scotland, but the brothers Thomas and George Duncan were born in Dublin in the 1850s-60s. George left for England as a young man. Thomas stayed in Ireland, but his daughter, Ida Coffin Duncan became one of the first women to practice as a barrister in the English courts.
Ida’s cousin Philip Courtenay Duncan was the second eldest of George’s four children (Philip’s older brother, Herbert, died in childhood). Richard Kemp has written an account of Philip’s tragically short military career, which can be found here.