My 14 month old son will walk, and even sometimes run, but when he is sitting or falls, for some reason he can't (or won't) stand up on his own. Is there a way I can encourage him to learn this vital life skill?

He also skipped the crawling phase, and still do this day cannot crawl (though he walks everywhere, grabs stuff, and even rearranges some of our furniture (dining room chairs) at times.