I am trying to remember the name of a young adult (possibly children) sci-fi book. The story has one main protagonist who is a young teen boy and it turns out he and his family are actually aliens. The boy did not know this and he is beginning a transformation. There is also a secret community of aliens. Some elements of the story are:
1.) There is a boy who, we are told, has his appendix burst but this was a cover up for his alien transformation.
2.) There is a glove (possibly metallic) which can be used by aliens (possibly a weapon).
3.) It is possible that the aliens, in their final form, were majestically blue (I can't be certain).
I read the book more than 12 years ago but I have no idea when it was published. Any help would be appreciated.