WGN is the short answer as to how I became a Cub fan.
I grew up in the Bahamas and lived there until 1986 when we moved to Canada. I had very little awareness of Baseball. I sort of knew about Reggie Jackson, but I remember trying to pretend I knew more about Baseball than I did by saying the Astros were my favorite team because Jackson played for them when of course I was confusing them with the Angels.
The Bahamas had a single TV station that didn't start broadcasting until 6pm. You could pick up TV stations from Miami with an antenna but the reception was often so bad that you all you could see was the visual equivalent of white noise. That changed in the early 80's when satellite dishes arrived on the island. These were big 15 foot dishes mounted somewhere in your back yard that you could illegally point at some unseen satellite and get access to crystal clear reception on 100s of channels. You had to go outside and hand crank the dish to point it at a different satellite for the first couple of years until we eventually got a motor that you could control from inside.
Anyway at 11 years old Scooby Doo was one of my favorite shows which WGN had on every afternoon after school; EXCEPT starting in spring I'd get home and there would be no Scooby Gang just...baseball?...everyday?...why weren't they playing at night? So at some point in 1982 I stopped being annoyed at the baseball telecasts and started watching. I remember seeing Junior Kennedy, Jerry Morales, Gary Woods, and Bill Buckner. I remember the final broadcast of the season as Harry congratulated Steve Stone on his first year in broadcasting and offered him some constructive criticism. By 1983 and the arrival of Ron Cey I was hooked. I guess it was excellent timing as 1984 was right around the corner.
My Dad retired in 1986 and we moved to Canada and there were some lean years as WGN was not available on cable in Canada until a few years later. Cubs have been constant since then. When I had an office job in Toronto my Supervisor often wondered why I'd take off a single day in early April every year. It was above his paygrade so I never told him and he never figured it out.