Ahem...Georgie boy, mad or no, didn't exactly like his siblings - he left his youngest sister in prison until she died (refusing to talk to her), he drew up the Royal Marriages Act due to his brothers marrying willy-nilly. Not to mention the women that became his sisters-in-law weren't exactly of his choosing/liking (for instance, Anne Luttrell-Houghton - "the Duke of Grafton's Mrs Houghton, the Duke of Dorset's Mrs Houghton, everyone's Mrs Houghton").
That said, his daughters that did marry, married as a way to escape their mother, whom they had to remain with as companions (much like Queen Victoria's). Elizabeth's statement of "if he is single, I will marry him" about the Landgrave of Hesse-Homburg, bears echoes of Princess Anne's remark about marriage to the Prince of Orange "I will marry him, even if he is a baboon". Elizabeth was forced to turn down a match with the future Louis Philippe, and Augusta was proposed to by both the prince of Denmark and Prince Adolf of Sweden, while Mary was wanted as a wife by Prince Frederik of the Netherlands.