i tried to sing [sign] up on his account with his data
I read that as jekaterina178 tried to sign into the dad's account with the dad's information. Anyway, trying to sign into the dad's account with jekaterina178's information would just result in signing into jekaterina178's account.
jekaterina178:
An "invalid" ID means something special. It is not a connection issue or a disabled account issue. If it was either of those you would see an error message about the issue, not "invalid". If you are sure you are entering his information correctly then you need to contact Apple as I instructed earlier since they may know why it is being listed as such. For example, if the account has not been used in a long time it is possible that Apple has deactivated it (this is mentioned in the iCloud terms of use document).