Connie find Firestorm as a hatching in a dark alley, injured and she took him home and cared for him. Then as Firestorm grew up, he and Connie became the best of friends and will always be there to help Connie out. And he often helps out the Riders on many of their adventures.
Firestorm was one of Connie's only friends when she was living in Manehatten. Connie treated and nursed Firestorm back to health when she found him injured in an alleyway and the two have shared an unbreakable bond since then. Firestorm could also type and do charades, so Connie could communicate with him, he is very protective of Connie.
Firestorm is also really close to Arnold and trusts him well enough to let him ride him. And he often watches how Connie trains him.
Firestorm also is really close to Yuna, and he respects her for teaching Connie the ways of the Force.