Many will consider this a little known fact of no consequence, but I was really excited to discover this.
Turns out that Inkscape will read and modify Microsoft Visio files. I've used Visio for many years for all my 2-D CAD work and have over 1200 visio drawings.
My sons don't have or know how to use Visio but they are knowledgeable with Inkscape which is open source and free. They will be able to view and change my visio drawings. I'm pumped.
Chuck