Visit Visa refusal - Pension Documents ! (insane)

[mm-2012]

Refusal letter :
“ I don’t see any issue from sponsor however sponsorship does satisfied me your own intention to leave the UK on completion of visit”
With above in mind , I have also considered the documents and information submitted with your application you have stated that you are married and you and your spouse intended to travel together and that you are in receipt of pension.
However, you have not demonstrated this from your supporting documentation and I have not been able to access how you maintain yourself on day to day bases. Given this I am not satisfied that you have accurately presented your circumstance and there for you intention to enter the UK. This undermines credibility of your application to extent that I am not satisfied with your application as per Paragharph V 4.2(a) and (c) of the immigration rules”

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Background - my Father in law is retired professor from state university and I have shared :
1. 6 month bank statement, showing the pension credit from “state treasury”
2. Explain the credit amount (pension, each month) in bank statement in the cover letter with “account head/item description” in the account as state treasury

This are the same document that I have submitted for my father and he has got the visa but father in law got the refusal.

So , I am confused as if one person gets the visa on the same set of document where as other person is rejected… so insane !

Please suggest what should I do i.e. documents that I can submit to get his visa pls !