The Guardianship of Children (Statutory Declaration Regulations 1998) have been revoked by the Guardianship of Children (Statutory Declaration Regulations 2020). The provides for a new Statutory Declaration Form for joint guardianship of a child which also facilitates same sex couples.
The Form is available here –
https://www.treoir.ie/wp-content/uploads/2020/07/NEW-Staturory-declaration-of-Joint-Guardainship.pdf