The Activation Lock cannot be bypassed - and if Apple Support have already declined to assist, you must either recover the original AppleID to which the Activation Lock relates, or accept that the locked devices are now beyond use.
These help pages may assist with recovery of the relevant AppleID(s):
https://support.apple.com/en-us/HT201365
https://support.apple.com/en-us/HT201441
You will ultimately be directed to this URL, from which you may be able to recover the AppleID and associated password:
https://iforgot.apple.com
To recover the AppleID, you will require access to either the primary email address associated with the AppleID account, any one of the secondary/recovery email addresses, or any one of the “trusted” telephone numbers (these may be fixed landline or mobile numbers). If you have access to none of these, then you’ve reached the end of the line.
Given the familial relationship, unless the AppleID account has been significantly neglected in its setup, you should be able to recover access.
Once you have recovered access to the AppleID account, you can change the email addresses associated with the account:
https://support.apple.com/en-us/HT202667
I hope this information proves to be helpful in recovering access.