My parents introduced me to tennis about 3-4 months before my 4th birthday. My dad said it's because he's a big fan of Mr. Roger Federer, but I think he got me started on it, because he got his butt kicked by my 72-year-old grandpa (to be fair, my grandpa was a nationally-ranked tennis player in Korea), and wanted ME to pay him back!
One of the benefits of living in NYC is having an access to a place like John McEnroe Tennis Academy, where they have world-class coaches and trainers. I first started in their Tennis Whizz program (3-5 year olds), but just after a few months, I was promoted to the Mac Red, then to Orange Club (7-10 year olds) for more advanced and serious players as the only 5 year old!
The program is on Saturdays, but my dad takes me to a public practice area near our home every morning with my brother to run all the drills I did in class, so that I don't forget what I learned from the coaches and master all the details. Of course, my 3-year-old brother is an excellent helper as a ball-boy.
By the way, I was thrilled that I got to see some of the greatest players in person at the U.S. Open last summer! My parents told me if I diligently keep up with the practice and stay focused, I may be able to play there one day. That would be AWESOME!