Couple apparently both over SRP still claiming UC

I have a client who is 68 and not eligible for a state pension as he does not have sufficient NI contributions. He and his wife claim UC and both claim PIP, and she gets CA for him. All fine and good if they are a mixed age couple, but client’s daughter swears her mother is 67 and not eligible for a state pension either. They are Irish, have lived in the UK for about 20 years, and both are illiterate.
The obvious explanation is some mix-up over the mother’s DOB, but before I open that can of worms is any reason why they could legitimately still be on UC and she be able to continue to claim CA?

There is absolutely no legal way that a pensioner couple can be entitled to UC beyond the end of the AP in which the younger partner reaches SPC age.  Something very wrong indeed here

But someone can continue to receive Carer’s Allowance beyond pension age, if their state pension is less than the amount of Carer’s Allowance.  But in this case, the client may want to relinquish it so that they can get double SDP in Pension Credit.