Does Medicaid frown on paid in-home care in lookback?

No. Of course not. People who are ill need care. Medicaid penalizes “gifting” for the five years previous to filing. If you are concerned about not having proper records, etc to prove how brother spent his money and your brother now needs Medicaid, I would suggest he seek the advice of a certified elder attorney.

Medicaid is a federal program that is administered independently by each state, therefore they can have their own rules and eligibility criteria on the application. It's best to inquire within your brother's home state.

Is he paying you?