How can I change DOB for someone in family sharing?

Hi! One of the people in family sharing, DOB is incorrect. When setting up the account, it got miss clicked. It was no big deal, as it was just a two year difference, until now. That person with the incorrect DOB, is 14 years old and is listed as 12, thus she cannot add her debit card to Apple Pay. This is a feature we really want her to be able to use. I have tried every article, disabling screen time, nothing allows me to change the DOB. When I contact support through chat, they have a ‘server error’ pretty quickly. Considering I have contacted support multiple times, I think they are giving up on me. I have done everything, but simply cannot fix this issue. Any help is appreciated.