My dad had a similar reaction to my second book - there were moments he said he teared up, too!
Both of their reactions mean so much, because it shows me they were invested in the story. They cared about what happened to the characters. If I had to choose one primary goal at all as a writer, it would be that one, I think. No -- not to make 'em cry (in fact trying to produce tears from readers is quite manipulative). But my goal is to make 'em feel moved. In this case, my friend's and dad's tears were evidence to me that the story reached through to their hearts.
That, I think, is a sign of success!
By the way, is it weird to admit that, sometimes when I'm re-reading/editing my OWN scenes, I tear up, too? I mean, I already know what's happening to the characters - I wrote the scenes! - and still, sometimes, I get affected by the work. Or, rather, by those characters (because they're so meaningful to me). I guess that's good!