I recently inherited my grandparents home. It is probably 65 years old with a concrete foundation and crawl space underneath. It was built on to about 45 years ago. The older part of the house has several cracks in the outside concrete foundation. I don't know if they are recent or have been there for years. I see none in the newer part of the home. Is this something to worry about? Should I fill in those cracks? Some of the cracks are a couple of inches wide.

Small cracks do not normally pose any problems. However if there is a large crack it could indicate the foundation/house has settled or that the earth under that part of the foundation is sinking. Only way to know for sure is to have it professionally inspected.

If you have cracks a few inches wide you are past the point of patching them. You need a pro to look at this and I think the correct repair would require jacking the house and replacing the complete foundation.