Mistakes on credit file

Equifax have put my brothers in laws current address in a section labelled 'linked address'
His credit card details are part of my husbands credit file with that address.
But they failed to check that both individuals have different full names different date of births so how can they link the addresses and use that as evidence to add incorrect items on his credit file
My brother in law has contacted Barclay card and has complained officially. He feels that this is a major privacy breach