Answer
7th is Hugh Grosvenor's title number, indicating his position as the 7th Duke of Westminster. The title of Duke of Westminster was created in 1874 for Hugh Lupus Grosvenor, the great-grandfather of the current duke. The title is hereditary, passing down to the eldest son of the previous duke. Hugh Grosvenor inherited the title in 2016 upon the death of his father, Gerald Grosvenor, the 6th Duke of Westminster.