Guy I work with had the same problem happen to him. Brother stole from mothers checking account, got credit cards in his brother name, stole items from his sister and sold them, etc... This went on for a couple of years, he kept promising that he had changed and apologized, but then it happened again and again. They finally got fed-up and pressed charges, went to jail, but he whined and his family felt guilty, so they bailed him out, got him a lawyer, of course they paid for it, and you guessed it. It started happening all over again! Once a scum bag, always a scum bag. I am a firm believer of an eye for eye, but beating him down is not going to solve anything, though it always does feel good. So yes, press charges and let him and his girlfriend rot. He (they) will say anything to get out of jail, don't let your feeling cloud your judgment or decision. Follow your gut in these matters, it will generally be a better guide.
As far as your credit, in this day and age you always have to be careful. Trust no one! You are allowed one free credit report a year and I highly recommend taking advantage of it. Just be careful where you get them from, some of the websites out there will promise you a free report but unbeknown-st to you, they enroll you into all kinds of things that incurre monthly/annual charges.
Check out this link, you might find it helpful:
The Federal Trade Commission's Information on Free Annual Credit Reports
