It would depend on the source of income and amount whether they were required to file or not. Only the court appointed representative if the deceased can access tax records or sign and file tax returns. You would have not obligation to become the executor unless it you need to in order to inherit any assets.
When asking about past tax going back years then professional help is recommended.
Suggest that you read IRS Pub 559 (Survivors, Executors, and Administrators) for a lot of good information about filing the final return and estate return and other requirements.
https://www.irs.gov/pub/irs-pdf/p559.pdf
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
