Tristan Kane is nice, a little bit trendy but at least not kre8yv.
Katherine Margaret is all right but very dull.
Charles is very nice and Charlie makes a friendly, good-natured kind of nn. I'm not crazy about Petra, it sounds like a cartoon or video game character, and I definitely don't like Quinlan, there's no strength to it.
As for Julie, well, from what I've seen of transsexuals and transvestites, I'm not surprised this just decided the make Julie be a feminine form of John. They tend to always want to be the center of the universe, so assigning a name a meaning it doesn't have so that it suits her purposes is about what I might expect. Ruthless stereotyping, yes. Not true in all cases, sure. But that's the first thing came into my mind.