I receive "Error -1005" any time I try to join a family with Family Sharing?

Hello arse_niiik,

This page can help out with providing some details on joining a Family Sharing group: Set up Family Sharing - Apple Support

If you can't accept the invitation

If you can't accept the invitation, check if someone else joined a family with your Apple ID. Remember, you can only join one family at a time, and you can only switch to a different family group once per year.

If the above note doesn't look to apply to the situation then you may try having the Family Organizer use the option for inviting in-person when sending the invite.

If you still need help you may use this link to try reaching out to Apple Support to investigate further: Apple Support

Cheers.