The 18th (Volume III, 1972) and 19th (Volume I - The Kingdom in Scotland, 2001) editions of Burke's Landed Gentry both purport to show Julian and the late Jeremy as the sons of Roderick by the late Mrs Hilary Burn-Callander (who, it appears, was Roderick's only wife). However, it would appear that they were Mrs Burn-Callander's sons by her first marriage (registered Q3 1946 - Hampstead) to Edward Dearden CARTER, and that they took their stepfather's name after his marriage to their mother in 1959.
The birth of Jeremy M D CARTER was registered in Marylebone in Q3 1949, and that of Julian T D CARTER was registered in Hammersmith in Q2 1954, the mother's maiden name in both instances being BRUNT. Per company records, Julian Thomas BURN-CALLANDER was born on 12 May 1954; his brother, Jeremy Mark Dearden BURN-CALLANDER, died aged 61 on 1 April 2011.