Gertrude Chastity and Gaylord Cannon Evans were born to Maria and Quentin Evans, second and third of seven, all of whom had the weirdest and most embarrassing name their parents could think of. Personally, GC no. 1 thinks she got off quite easily, compared to Gaylord Cannon, whose name had to have been a joke. The siblings are half-bloods, with a pure-blooded mother and a muggle-born father, and grew up knowing more about the muggle world than most wizarding children, apparently.
GC spent most of her childhood playing chaser or trying to hit bludgers hard enough to make them move, which apparently amuses EQ. Of course, she's now a lot better at it, but she thinks she'll stick to chasing. The Evans household was managed by magic, unless the kids managed to anger their mother enough to be subjected to that which they dreaded most - chores. For their first seven years or so, the GCs went by Gertrude and Gaylord, until Gertrude decided she didn't like her name and followed EQ's example by restyling herself as GC, and Gaylord realised what his name meant and immediately followed suit.
GC's first sign of magic was when she was eight years old and her twin wouldn't give back her Holyhead Harpies figurines. Getting worked up, she accidentally caused a heavy hardback to fall on his head and he may or may not have ended up with a small concussion, which she still likes to bring up whenever he teases her.