Family sharing issue
Why does my daughter keep getting this message when trying to accept my family sharing invitation “the operation couldn’t be completed. (Com.apple.family.error error-1005)
For that kind of numerical error I suggest you contact Apple:
Refer to this document for ways to contact Apple --> Choose your country or region - Official Apple Support
Select your country (also look for "other" regions), then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service by telephone --> Contact Apple for support and service - Apple Support