Son is an individual account owner.
Son's Father is an authorized signer.
Son's Grandfather is an authorized signer.
Father takes Grandfather's debit card and makes purchases and ATM withdrawals.
Grandfather has since passed away.
Son claims the debit card purchases and ATM withdrawals made by his Father using his Grandfather's debit card were unauthorized.
Can the Son be held liable since the Father and Grandfather were authorized signers on the account?