I've been going to see Yankees games in the BX since I was 3, and that team had been my sole 'sports identity' for my whole life - I liked other teams here and there but once a Yankee, always a Yankee. In the early 2010s my wife and I started to get into Premier League football, and footy in general. By 2014 I knew I had to pick a squad for both the Prem, and a main one globally, and lo and behold, NYCFC came along: they played in my home/church, had great colors and players, and were connected to a team I had started a predilection for since 'AGUEROOOOOOO' - MCFC.
Now, even though I still love the Yanks with all my heart, NYCFC has become by #1 passion and love. I became a Founding Member during the first season, and still hold on to that status, mainly to get 'my brick' in a new stadium (whenever that happens.) I live in Phoenix Arizona now, and have for the last 10 years or so, so a season ticket is more of a pain than anything (as I have to sell it each match, and usually at a bit of a loss) but I'm still really proud of the association either way.
Hope that helps !