They could do the Scottish thing and make the Scottish title inheritable by women. So if Harry and Meghan only have daughters, Sussex would go extinct, but the eldest daughter would be Countess of Dumbarton. There is definitely precedence in Scotland for that. In fairness they should have to offer Andrew to do the same, so that Bea could inherit her father's earldom at the least.
Honestly they should
1. Make all future titles equal inheritance
2. Make it clear to any peerage who wishes it, that they can appeal to the queen to change the letters patent on their title which she can do, with the assurance she will. So that any old peerage, who wishes their daughter to be able to inherit, can.
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Point #1 - I agree wholeheartedly. And if York does go to one of William's children (which I don't think it will), it should be Charlotte not Louis. If Louis gets a hereditary dukedom/earldom/whatever, so should Charlotte. Princess Royal isn't enough. It's technically a
style, not a title, and it's not hereditary.
Point #2 - It's not that simple. While the Queen has the power to grant titles to members of the Royal Family, she cannot give titles to non-royals without the advice of her Prime Minister. The same holds true for peerage claims. She must rely on the advice of her Attorney-General. In terms of contentious claims, the Attorney General generally recommends that the monarch refer them to the House of Lords.
Think about it...if the Queen does have the power to alter a title's letters patent, why aren't the peers who DO want their daughters to succeed them appealing to her instead of Parliament?
See, for example, the case of the 8th Earl Fortescue, who only has daughters and isn't happy that his title will go to a male cousin:
https://www.independent.co.uk/news/...ts-battling-to-inherit-the-title-8656310.html
I may be wrong, but I'm not even sure the Queen has the power to change letters patent for royal titles once they have been issued. Why else would she ask Charles to create his brother Edward Duke of Edinburgh when he becomes King? Why doesn't she just change the current letters patent and allow Edward to inherit the title when Philip dies instead of Charles? It seems that in order for Edward to become Duke,
new letters patent are required and that can only happen when Charles becomes king and his Edinburgh title merges with the Crown.