tenants adult children

Other

I have a tenant who when at start of tenancy 3 yrs ago had 2 dependant children, approx 16 and 17, they are not named on original AST. The daughter moved out and had a child (who unfortunately has severe health problems) the son now has a job. The current situation is that they now are all back living at the house and the Mum is off sick with stress and only entitled to stat sick pay so has contacted me to say she cannot pay the rent. She will be 2 months in arrears on 1st March, I have spoke with her and have told her i cannot afford for this situation to continue and will be forced to present her with Section 8 notice at beginning of March. My query relates to her now adult children and the disabled grandson, are they squattors and how will this situation be dealt with by the courts. We have been through the process before so I suspect Housing Benefit/ CBA will advise to sit tight until CCJ issued, just concerned by the complicated "extras".