Okay, I haven't seen the wellness skill come up on this topic but it might be somewhere else so apologies if it's a double post.
I just wanted to point out that if you have your teen sim learn the wellness skill and you have a parent that has the vicarious trait, it doesn't flow on.
To give an example using the Landgraab family: Say Geoffrey (adult) has the vicarious trait and Malcolm (teen) learns the wellness skill via the books, Geoffrey won't learn the wellness skill unless he too reads the books or attends the spa. whereas say, Malcolm learnt the gardening skill, Geoffrey could learn the gardening skill via the vicarious trait instead of the books.
Hope that is useful info for someone out there..