I started out as a fan of the music.  I actually attended my first Nelson concert in Boston in the early 90s before I knew anything about them...and I just loved their songs and their show.  But then, several years later, I met them and learned that not only are they wonderful musicians, they are terrific people.  They're nice to all their fans, even when they're tired and what they really want to do is just switch over to personal time.  One of the most thoughtful things I've seen them do happened at EPCOT several years ago.  Matthew and Gunnar were headed into the park and toward the stage, but stopped to say hi and give me a hug.  It was a really hot day and I was pretty sweaty.  They reminded me that I needed to stay hydrated, and then brought out a basket containing water, soda, and cups of ice for the few of us that were standing in line.  I already knew what great guys the twins are, but the few other fans there in line were surprised by their thoughtfulness and couldn't say enough about them to everyone else who joined the line.  They earned a lot of new fans that day. 
In the last several years, I've enjoyed the different kinds of music Matthew and Gunnar have played with their various bands.  I love when they play their father's music, but I was thrilled that they've started playing as Nelson again.  I really enjoyed the Red37 CD, though I haven't had a chance to see them live.  And it's a blast going to Scrap Metal shows, hearing them play and sing other groups' songs.
How could I not be a fan of two guys who are so talented, but also generous with their time and their support of charitable causes?