What is the name of Queen Elizabeth II's cat?

Queen Elizabeth II received a Siamese cat for her wedding and named it "Corsham Royal Boy."

https://www.pumpkin.care/cat-breeds/siamese-cat/

Are you referring to Sybil, who in 2007 was named Chief Mouser in 2007? Although she is the "first cat" at 10 Downing Street, she isn't actually Queen Elizabeth's cat, rather she is "officially" employed by the Queen.

https://en.wikipedia.org/wiki/Sybil_(cat)

Everything I could find never mentions her getting another cat, just all her corgis. I doubt Royal Boy is still alive since QE2 got married in 1947!

This Buckingham site paragraph presents a real possibility that the Queen has a number of personal cats:

The Royal Mews (No, it isn't where the Queen keeps the royal cats) on the south side of the palace is worth a look if you have time. Here is where the collection of Royal carriages are kept.

http://www.hotels-london-hotel.com/buckingham-palace/


But what are their names?

Hello Magazine states in 2020 that only one member of the royal family has a cat - Prince Michael of Kent.

https://www.hellomagazine.com/royalty/2020101599146/only-royal-family-member-owns-cats/