Carers allowance and EU coordination rules

Client dual citizenship, Polish passport and British passport. Is looking into what help may be available for looking after sick parent in Poland, parent has always been in Poland.
I’ve looked at carers allowance, but presume, AA would need to be claimed by parent to enable this to happen. Parent claims Polish pension, but no Polish sickness benefits I’m aware of.
Would the competent state likely be Poland, for the parent and so no claim for AA can be made?
I’ve confused myself over family rules, client been in the UK for over 15 years and knows little about polish sickness benefits - neither do I
All comments welcome

1. For Polish parent- looks to me like Poland is the competent state for any claim to a cash sickness benefit such as AA - so no route to AA.

2. Client could still potentially try to claim CA if could argue that parent in Poland was getting a Polish equivalent to AA I think - see article 5 of EU Regulation 883/2004 which provides “where under the legislation of the competent MS [UK for purpose of her claim to CA] the receipt of social security benefits and other income has certain legal effects [eg under UK legislation receipt of AA allows carer to get CA] the relevant provisions of that legislation shall also apply to the receipt of equivalent benefits acquired under the legislation of another Member State….”- however doing so is likely to involve a long and tortuous fight….