Brighty isn't related to the royal family, but she may as well be a part of it. She's part of a small team of guards around the royal grounds who, well, guard the royal grounds. As I said, there isn't much conflict in Chao World so extreme defenses aren't really required. Brighty's job is mainly to just make sure nobody's screwing around and committing petty crimes like vandalism on the property. Her skills also obviously extend to the water, so she's also capable of easily checking up on dams and moats and whatever other watery things need to be supervised. All that being said, she is the typical lazy fall-asleep-on-duty guard. Not that she doesn't care about her job; she just gets comfortable very easily. If a job needs to get done, she will take care of it. She's tough, sturdy, and can be really scary in the right situation. Her fellow guards are still seen as more capable, but she doesn't really care about that.
Brighty is, by definition, a bright and happy individual. She has fun with everything she does and is pretty self-indulgent. She's reckless and doesn't tend to hesitate or second-guess herself about things, which can be both good and bad. But Brighty is also very down-to-earth, in any case, and is a really genuine person. Her kind of abrasive and boisterous personality is kind of off-putting to some, especially the uptight royal family. They can't do anything about it, though, because she's such close friends with Pilvi.
(Once I make a proper reference sheet for Brighty, I'll replace the current image with that. Also the height and weight are temporary until I actually put some thought into it.)