Can my 12 year old have Apple Pay?

Set up and use Apple Cash Family - Apple Support

https://www.apple.com/apple-pay/

-- fine print at at the bottom" "To send and receive money with Apple Pay or receive the Apple Pay Cash card, you must be 18 and a U.S. resident. Services provided by Green Dot Bank, member FDIC. Security checks may require more time to make funds available."

If you are talking about regular Apple Pay (adding a debit card) you must be 13.