hi i had gone through your query and understand your concerns. i would come up with the possibility of RHEUMATOID ARTHRITIS
may be the cause for his sufferings.
-it is an autoimmune disease
often run in families.
for positive RA factor ( may be negative also ),increased CRP,ASO tritre,ESR
may confirm the diagnosis.
i would suggest you taking Homeopathic
medicines gives safe and permanent cure for his arthritic complaints
consult your local homeopathic physician for correct diagnosis of the case and remedy to fit his complaints
I hope this is helpful for you, thank you