The Majestic Titles Decree concerns the usage of the styles and titles of the Monarch, their spouse, their mother. The Royal Titles Decree concerns the usage of the styles and titles of members of the Royal Family.
Notably, the mother of King Matthew is entitled to use the style and title of Her Majesty The Queen Mother, while his father holds the style and title of a Prince. Also of note is that King Matthew's grandparents have been granted the styles and titles of Prince and Princess.
Also entitled to the styles and titles of Prince and Princess are the Monarch's children, grandchildren, and great-grandchildren, as well as King Matthew's siblings, nieces, and nephews.🎺