Your mother wants access to her content. Same with my partner Ruth. She is happily using CentOS (with the Stella repositories for multimedia) on an X61s with Ultrabase for surfing and watching videos and DVDs. It gets the job done, and I had the Thinkpad around anyway when her iBook stopped working.
Does your brother need access to specialised software (e.g. having to hand in College/University work in some Windows specific system or using business applications)?