I am disabled and have retirement benefits also. My two grandchildren are living with me, so do I need to file a tax return?

There's no way to know based on what you said. Are your grandchildren minors, or in college?
There are at least a dozen questions to ask.

Gather all your papers together and take them to a tax preparer, or possibly a senior center. Often there is free help starting in about 2 months, sponsored locally or through AARP.

You need to determine total income and see. Is anyone else claiming the children on their return? Depends on age, whether a widow or widower. Check with senior centers. I have mine done free through an AARP program and the county where I live.

If the retirement benefits are taxable, then likely a tax return is required, and you will gain a benefit by claiming your two grandchildren.

However, if the retirement benefits are tax-exempt due to your disabled status, then no tax return should be required. It may be possible for someone else in your family (the children's parents come to mind) to claim the grandchildren on THEIR tax return.