Tenant has previous property rent and council tax arrears

Hello,I would be grateful for any advice.

This situation is quite complicated at the moment as I currently do not have the full facts.

My brother has recently moved back into my mothers home (I dont live there) and I have since found out that a bailiff has issued a citation in my brothers name for rent and council tax arrears from his previous council property.I would like some advice if this would affect my mothers tenancy in anyway? or if she would also be held liable for arrears from my brothers previous property?

Currently I dont have all the facts as I'm still trying to get all the information in regard to this,I am not currently sure if my mother has put my brother as a joint tenant or if he is just a resident for rent and council tax purposes.I have also found out that this situation happened previously around 4 years ago and my mother had to pay outstanding arrears of around £1000 from my brothers previous home at that time.

I would also like to add that my mother has mild learning difficulties and it is quite possible that she has unwittingly put my brother on the tenacy agreement thus will now be liable for any his rent arrears from his previous property.

any advice and guidance willbe gratefully received