2Tracy Sister- Thunderbird Fanfiction » Sky Tracy is my OC and so are the other characters, but Thunderbirds don't belong to me. This is based on the characters in the movie and my own twist on it. So what if the 5 brothers had a sister?A sister who loves animals and a special talent. Matter of fact Gordon twin sister. Also what if Lucy( the mom) left a surprise in an abandoned hanger just for her daughter?