PENSION CREDIT AND SEVERE DISABILITY/CARERS PREMIUMS.

I have a client who gets Attendance Allowance and lives with her Grandson who gets MRC DLA and LR Mob. , he is 25. Can they claim CA for each other ?(as a married couple can when they live together) . Client is 77 also gets PC Guarantee Credit and Council Tax benefit alongside SRP and Occ Pens. No savings.
If this can be done- Grandson would get the CA and would this be deducted from ESA that he gets and she would get U/E entitlement to CA , would this give her the Severe Dis Premium and the Carers Premium for her Pension Credit?  Can this be done , and does it have any disadvantages for either client or grandson?
Thanks for any help received.

It’s ok I have sorted it out. Thanks to all those who looked.