Any such restriction would quite routinely be rather ridiculous since: (1) there are many millions of families where some/most/all persons in a family have different last names from others in the same family/family household; and/or (2) there are many people who are immediate family members who share the same last name and may or may not even live in the same household but are unable to make an independent declaration.

A better standard to be examined is that of allowing joint processing as a product of there being joint and several liability -- or willful assumption of such liability -- if someone/some party wants to risk liability for a violation of persons party to a joint declaration, then that should be their business; and that allows for anyone and/or the entire party agreeing to take such liability/risk on entry by choosing to be processed jointly.