Sometimes it just irks them. I know I couldn't persuade my brothers to try the course if hell froze over. The idea of relearning something they had a hard time with at school in the first place... well they'd knock my block off for suggesting it.
Sometimes the best way to help them is let them find it themselves. EG you leave the book lying around and make a fuss about misplacing it... like its worth it's weight in gold or something... Pick up a book and just mention that you are going to start reading it... come back in an hour or so later and say something in passing about the book and toss the book back on the coffee table. Lay the bait.
Now something like that might work for you. You know them better than I would. Me on the other hand, I haven't even told them I did the course.
If they are closed minded you can't force it.. that backfires big time. Accept it with a shrug of the shoulders and say fine. It hard knowing you not helping family and friends. If you force the issue they feel like you're trying to sell them an MLM scheme and resent you for it.
Alex