I was 30 before I took my first course in "relationship communication" (that means I was married for 12 years by then!). I took some pretty intensive courses. Such courses as "Human Interaction Lab" and "Dealing with Power and Conflict Lab". When I was finished that series of 6 over the course of a few years, I plunged into Reality Therapy and Choice Theory Training.
All of this training was interactive - that means there was lots of "on the ground" feedback about my own behavior and communication skills as we practised our skills to use back in the real world.
But even with all of that training and feedback it took me awhile to 'get it' when I got home and remember to put it into use.
My first job in this area was teaching the skills at a community college to business students. I remember a day when I was teaching my students how to give effective feedback (no global statements, use "I", don't blame just describe the situation etc). I went to bed that night just before my husband. Then he came into bed and left the bathroom light on (as was his habit). I roused myself enough to say "You ALWAYS leave that damned light on. Can't you EVER learn to turn it off????"
And then I heard myself, doing all the things I taught my students not to do in one statement!!! The light bulb went on in my mind! I was teaching it but I wasn't using it! And that was the turning point in my journey to better communication.
Relationship communication and behavior can be learned at any age. If some of us were lucky enough to have good role models as children, that's great. If others have to take training as an adult, good on you! Go for it! It changed my life and made it so much happier!