He was the son of Charles, 3rd Marquess of Londonderry and his second wife Frances Anne Emily Vane-Tempest, daughter and heiress of Sir Henry Vane-Tempest, 2nd Baronet.
As Viscount Seaham, the future Marquess married Mary Cornelia Edwards, daughter of Sir John Edwards, 1st Baronet, on August 3 1846. They set up home at Plas Machynlleth, the Edwards family seat, and had six children:
Viscount Seaham managed Sir John's estates, which included some of the slate quarries around Corris, and was one of the original promoters of the Corris Railway, created to carry the slate from the quarries to the markets. He became Earl Vane on the death of his father, and under that name sat on the board of the Cambrian Railways, latterly as Chairman. When his half-brother died childless he inherited the Londonderry estates and titles.
His eldest son left Machynlleth on succeeding to the Marquessate, but his youngest son, Lord Herbert Vane-Tempest, remained resident at the Plas, and also served as Chairman of the Cambrian Railways, until he was killed in the Abermule train collision. The family gave the Plas to the townspeople after World War II.