This is another topic which has always interested me, and I share it in case anyone else finds it of interest.
"The Ladies Waldegrave" (the title of a famous Sir Joshua Reynolds painting of them) were the three daughters of the 2nd Earl Waldegrave (1715-1763) and of his wife, Maria Walpole, who later married the Duke of Gloucester.
Each wound up marrying what must have been considered perfectly good matches: one married their cousin, the 4th Earl Waldegrave, one married the 4th Duke of Grafton, and one married Lord Hugh Seymour.
Yet in 1780 Horace Walpole could bemoan the fact that within the preceding year all three had missed out on quite spectacular matches. As Walpole wrote on 24 July 1780:
“Still these three charming girls inherit more of their mother's beauty, than of her fortune. Each has missed one of the first matches in this country; Lady Laura Lord Carmarthen, Lady Maria Lord Egremont, Lady Horatia the Duke of Ancaster, after each had proposed and been accepted! The fate of young women of quality is hard: in other countries they are shut up, till their parents have bargained for, without consulting, them. Here they are exposed to the addresses of every coxcomb that has a title or an estate to warrant his impertinence."
1. Lady Elizabeth Laura Waldegrave (25 Mar 1760-Strawberry Hill 29 Jan 1816); m.Gloucester House, London 5 May 1782 George Waldegrave, 4th Earl Waldegrave (23 Nov 1751-22 Oct 1789); she had first been engaged to the Marquess of Carmarthen, but the match was called off because the Duke of Leeds could not make a proper settlement, because all the estates were already entailed on the children of the Marquess’s first (dissolved) marriage.
I could find no correspondence related to this match, except in a footnote written by Walpole himself to the letter to Mann, 24 July 1780:
"The marriage was broke off, the Duke not being able to make an adequate provision, Lord Carmarthen having children by his first wife, on whom the whole estate was settled."
(When I was looking for information about this, I came across an interesting note about the eternally eccentric Lady Mary Coke, when Carmarthen finally did marry again:
Walpole to Lady Browne, 27 September 1788:
"Lady Anne [Connoly] has told me too, that Lady Mary Coke, from want of food for her anger at this dull season, is exceedingly enraged at Lord Carmarthen's match, and I suppose imputes it to her friendship for Lady Holderness [mother of Carmarthen's now deceased but previously divorced ex-wife], who I dare to say is perfectly indifferent whether she is angry or pleased.")
2. Lady Charlotte Maria Waldegrave (11 Oct 1761-1 Feb 1808); m.1782 George Henry Fitzroy, 4th Duke of Grafton; she had first been engaged to the extremely wealthy Earl of Egremont, but she called off the match, not liking his behavior.
Walpole to Mann, 6 July 1780:
"Lord Egremont, who has for some time been in love with my niece Lady Maria Waldegrave, the Duchess's second daughter, has at last had an audience and demanded her. He is eight and twenty, is handsome, and has between twenty and thirty thousand a year. You may imagine he was not rejected by either mother or daughter. The daughter, with a charming person, is less beautiful than either of her sisters, though more liked by most men. She has spirit, a great deal of wit, and the sagacity and good sense of her father, with constant good humour and cheerfulness. We are all happy with this alliance, and Lord Egremont's family shows general satisfaction. I, who live to see so many strange events, did not expect formerly that Sir William Windham's grandson would marry Sir Robert Walpole's great-grand-daughter, to the equal content of both houses.
The Duke and Duchess with the little Prince and Princess, the bride, her sisters, Lady Egremont, and her son the bridegroom, were all at Ranelagh together last night. I satisfied myself with seeing them at Gloucester House before they went. The company, I hear, were pleased with this exhibition; and, in truth, it was worth seeing."
Princess Augusta [aged 11] to Mary Hamilton, 17 Jul 1780
"Lady Egremont told the Queen that she now is perfectly happy for Lord Egremont is for certain to marry Lady Maria Waldegrave."
Walpole to Mann, 24 July 1780:
"I must notify the rupture of our great match, which I announced in my last. Lord Egremont, who proves a most worthless young fellow, and is as weak and irresolute, has behaved with so much neglect and want of attention, that Lady Maria heroically took the resolution of writing to the Duchess who was in the country, to desire her leave to break off the match. The Duchess, who had disliked the conduct of her future son-in-law, but could not refuse her consent to so advantageous a match, gladly assented—but the foolish boy, by new indiscretion, has drawn universal odium on himself. He instantly published the rupture, but said nothing of Lady Maria's having been the first to declare off—and thus everybody thinks he broke off the match, and condemns him ten times more than would have been the case if he had told the truth—though he was guilty enough in giving the provocation. We are all charmed with the sense and spirit of my niece, who would not risk so probable a chance of unhappiness, though the fortune was so great, and she could not dislike his person.”
Lady Sarah Lennox to Lady Susan O'Brien, 1780:
"Lord Egremont has long professed to like Ly Maria [Waldegrave], but never could bring himself to propose in form. During this time the Duchess of Gloucester abused him continually in the most publick manner, which did not encourage him to have any dealings with her, but however love, or whatever you please to call it, got the better, & he did propose; he wanted to be married in a moment, but Ly Maria being a ward of Chancery it was impossible to marry on articles. During the courtship all his family show'd the greatest joy and attention to the Waldgraves; the Dss of G. was pleased with all but the man, whom she had taken in aversion, & went so far as to say she would show her dislike to him by quarrelling with him the moment he was married. There goes a story that she required 6,000 a year jointure for Ly Maria, but I fancy that is not so, & if she did it was only to put off the match. Now whether it is her behaviour that is the cause, or that other people have got round him & persuaded him to break it off, or whether it is really & truly (as he says) only his dread of not making a good husband, I leave you to determine, but so great is the influence that this cause has upon him that he took the resolution of going to Ly Maria & telling her, "that he was certain he should be miserable to be married, because he felt himself unequal to making her happy, but that if she chose it he would marry her? She very properly resign'd all claim to his word, & did it "like an angel, & without a reproach"; this is his own words. He accuses himself of being mad, says he has used her cruelly, but that it's less cruel to leave her free than to neglect her happiness when she is his wife. He speaks of her in the highest terms, this he did to my brother, so I can vouch for the truth of it, & I am glad I can, for it takes off a little of the shamefullness of his conduct."
3. Lady Anne Horatia Waldegrave (1762-12 Jun 1801); m.2 Apr 1786 Lord Hugh Seymour; she had first been engaged to the Duke of Ancaster, who died aged 22 before the wedding could take place
Walpole to Mann, 9 July 1779:
"The Duke of Ancaster is dead of a scarlet fever, contracted by drinking and rioting, at two and twenty. He was in love with my niece Lady Horatia, the Duchess's third daughter, and intended to marry her. She is a beautiful girl, like her mother, though not of so sublime a style of beauty. I much doubt whether she would have been happy with him, for though he had some excellent qualities, he was of a turbulent nature; and though of a fine figure, his manners were not noble."
Walpole to Lady Ossory, 14 July 1779:
"Are not you sorry, Madam, for the poor Duke of Ancaster, especially since he made so noble and sensible a will? I think his attention to his mother must half kill her. I hear he has left a legacy to a very small man that was always his companion, and whom, when he was drunk, he used to fling at the heads of the company, as others fling a bottle."
Walpole to Mann, 16 July 1779, added as postscript to a letter dated 30 Jun 1779:
"The Duchess Dowager of Ancaster, Lady Elizabeth Burrel, and the new Duke and Duchess have all written to Lady Horatia, acknowledging that the late Duke was to have married her. The two first have expressed themselves in the tenderest manner; the others wrote only for form. The mother Duchess approves of my niece going into mourning, which she does for six months. The poor young man, his father's absurd will not standing good, made a new and most rational one four years ago, in which he gives the seat of the family and £5000 to the present Duke and to the title, and adds £1800 a year to his mother's jointure. Such symptoms of sense and feeling double the loss."
Walpole to Lady Ossory, 20 July 1779:
"It is true that my niece Horatia has put on mourning for the Duke of Ancaster: it is on precedents, and with the approbation of the Duchess Dowager, who has written to her in the kindest manner, acknowledging the intended marriage, lamenting not having her for a daughter and offering to come to her as soon as she is able. Lady E. Burrel has written in the same style; and the new Duke and Duchess have sent compliments of condolence. Lady Horatia has behaved in the most reasonable manner, shown very proper concern, but nothing romantic or extravagant."
Lady Sarah Lennox to Dowager Dss of Leinster, 12 Aug 1779:
"Lord Egremont's match is still in statu quo. Poor Lady Horatia has been very ill with her grief for the loss of the Duke of Ancaster to whom she was to be married immediately. She mourns for him and is treated by his family with every attention that would have been due to his widow; poor thing it is a sad stroke so early in life, but I think one may almost see it was for the best. Which is what I always believe of every misfortune, but it is not always so visible. He had some very good qualities, but drank so hard as to ruin his health if he had lived; and in that case she has many years of sorrow swallowed up in one great affliction."