On 8 July 1740, he married Catherine Conduit[1] (d. 15 April 1750), the daughter of John Conduitt and great-niece of Isaac Newton, by whom he had four sons and a daughter:[2]
John Charles Wallop, 3rd Earl of Portsmouth, born 18 Dec 1767, died 14 Jul 1853, married firstly, Hon. Grace Norton, daughter of Fletcher Norton, 1st Baron Grantley, and Grace Chapple, he married secondly, Mary Anne Hanson, daughter of John Hanson
Newton Fellowes, 4th Earl of Portsmouth, born 26 Jun 1772, died 9 Jan 1854, married firstly Frances Sherard, daughter of Reverend Castell Sherard, he married, secondly, Lady Catherine Fortescue, daughter of Hugh Fortescue, 1st Earl Fortescue and Hester Grenville
Urania Catharine Camilla Wallop, born 23 Nov 1774, died 2 Jan 1815, married Reverend Henry Wake, son of Rev. Dr. Charles Wake and Barbara Beckford, daughter of William Beckford
Major William Barton Wallop, born 24 Dec 1781, died Dec 1824, married Elizabeth Ward, daughter of Major Ward
Hon. Bennet Wallop (29 January 1745 – 12 February 1815), married and had issue
Caroline Gordon, born 1772, died 13 December 1801, married Lt Col. William James, son of Lt Col Charles James and Catherine Napier, daughter of Sir Gerrard Napier, 5th Baronet and was grandmother to Canon Mark James
In 1741, Wallop was returned to Parliament on his family's interest for Andover;[1] he and John Pollen defeated William Guidott and John Pugh, the former a local official and former MP who had gotten himself disliked by the Andover corporation.[4] Wallop was likewise returned for Whitchurch, where he had inherited an interest through his wife, but chose to sit for Andover.[5]
He sat as a Whig, supporting Robert Walpole's administration, and voted for Giles Earle in his unsuccessful candidacy for chairman of the Committee of Privileges and Elections that year. He abstained from the vote to investigate Walpole's conduct in 1742. In 1743, his father (who had lost a number of local offices in Hampshire on Walpole's fall), was created Earl of Portsmouth, and Wallop adopted the style of Viscount Lymington. He voted against the Carteret Ministry in 1744 on their bill to hire Hanoverian troops for the War of the Austrian Succession.[1] Lymington was considered a supporter of the Pelham government in 1747, when he and Pollen were returned for Andover without a contest.[4] Lymington died in late 1749, in the life of his father.