EEA Family member failed HRT for UC claim

Hi all, I hope you can help

I have a client who came to the UK in Jan 20 under an EEA family member visa. he is an Indian national with severe learning difficulties. He came to the UK to live with his brother who was a Belgian national who had been working in the UK since around 2007. The brother was stopping work to become his full time carer but had already been granted a Permanent Residence visa.

Pre-Settled Status was granted to my client and the brother then applied for and gained a British passport (in Dec 2020). Then in Jan 21 the brother applied for UC with a fit note for my client, which was refused under HRT rules.
So, at the point my client claimed UC his brother had already been granted a British passport.

The question therefore is, is my client still an EEA family member of someone with a Permanent Right to Reside in the UK - because his brother still holds a Belgian passport as well as the British passport - or does the British passport mean that the brother is no longer an EEA national in the UK.

Currently the only income into the household is my client’s sister-in-law’s wages. She is also a Belgian national, with a permanent to reside, but who also obtained a British passport.

Many thanks

There is a case on this called Lounes. An EEA national who becomes a permanent resident of the UK and subsequently naturalises as dual national British can still rely on their rights to be accompanied by family members. This is reflected in the amended definition of an EEA national in the Immigration (EEA) Regulations. See also ODS v SSWP (UC) [2019] UKUT 192 (AAC). Provided that your client meets the definition of a family member or extended family member of the brother, they would have a right to reside.

Many thanks @Elliot, this is extremely helpful!