Many genealogies including Burke say that Mary Brabazon daughter of Chambre 5th Earl of Meath married Rev William Tisdall but Mary actually died unmarried in January 1737/8 aged about 55 and was buried next to her father in St Mary's Nottingham. There is a monument, there to her.
But another younger Mary Brabazon did Mary Rev William Tisdall jnr. in St Peter and St Kevin Dublin on 20 May 1734. She was supposed to inherit real estate from Chaworth 6th Earl of Meath (in his will made 1747) but apparently was dead before him. Mary seems to have had at least one child, Brabazon Tisdall christened 3 July 1735, St Peter & St Kevin, Dublin, and probably a daughter, Mary.
ATTACHMENT - MEMORIALS OF AN ANCIENT HOUSE
Tisdall, dau. Rev. William Tisdall. B.A., Rector of St. James's, Dublin, by his wife Lady Mary Brabazon, second dau. Chambre, 5th Earl of Meath.1 This lady had been brought up in the Earl of Meath's house under the following circumstances:—<€ It appears that her mother. Lady Mary Tisdall, had a devoted friend in Juliana, dau. of Sir Thomas Prendergast, Bt., who married in 1731 her brother Chaworth, 6th Earl of Meath. The two girls arranged before marriage to exchange first children. The Countess of Meath, however, had no children, but her friend gave her her eldest daughter, Mary Tisdall in fulfilment of the compact." Lord Meath intended to leave most of his property to his adopted daughter, but died intestate. A collection of medals and curios, which he had given her, was sold for £10,000. William Lyster had issue by Mary Tisdall four sons and a dau:—
But who was she??? Could she have been Chaworth's daughter? by the chambermaid?
The story in the attachment says that Mary Brabazon was a friend of Juliana Prendergast (who married Chaworth in 1731). The story of course is incorrect at least in saying that Chaworth died intestate.