Hi DC
Yes it is correct, it is classed as an overlapping benefit, your father has an underlying entitlement to carers allowance.
Depending on your parents income, if it is less than (£346.60 + £46.40 Carer element due to underlying entitlement = £393.00 per week) then they would be eligible to claim Guarantee Pension Credit.
We would advise your father to seek help from your local Welfare Rights Specialist; you can find your local Welfare Rights Organisation to help you with advice by clicking on the link below and putting in your post code, it will then come up with a MAP with a list of agencies in your area
advicelocal.uk .
Gary