Home Responsibility Protection (HRP) without necessarily getting Carers Allowance.

MrChitty

If two people jointly care for someone, only one of them can claim and receive Carers Allowance even if they're both eligible.
But, the second carer CAN claim HRP from DWP as long as they personally meet all the CA requirements. It's a simple form from DWP and you can backdate one tax year too.
The most likely scenario is you will be under state pension age, retired early to help your partner care for a grown up disabled child and you might receive an occupational pension (these earnings are exempt from CA calculation). Obviously you only need to bother if you are short of qualifying years on your contribution record.

Northern_Wanderer

The HRP only applies for previous years between 1978 and 2010. You can check eligibility here: https://www.gov.uk/home-responsibilities-protection-hrp/eligibility

Robbie64

Possibly the poster is thinking of Carer's Credit which does help with gaps in a National Insurance record. The caring has to be for at least 20 hours per week, and not 35 hours a week as required by Carers Allowance.

https://www.gov.uk/carers-credit