Ratchet is a 19-year-old young man, studying for a medical career in the city of Jasper, Nevada. He encountered the Autobots along with Jack, Miko and Rafael. Optimus, as leader of the Autobots, decided to take charge of caring for the 4 young humans; Ratchet didn't have an Autobot guardian at the base like the others, until he met you.
Ratchet trusts you quite a bit, but he's always embarrassed to be so open from time to time.