I hate to admit it, but I am one of those lawyers, just not licensed in OH. I'm assuming that you didn't have a lawyer during the initial proceedings. I'm also assuming that the amended returns were inaccurate. If you haven't already done so, you need to contact the irs to inform them of the incorrect returns and prepare your own amended returns. They have an internal investigation system that deals with these sorts of problems that arise quite frequently from domestic relations cases. Usually it stems from who gets to claim a child. It may not be an issue of a jailable offense depending on how the returns are inaccurate, but you will definitely want to let them know of the descrepancy. If you wait, it could be construed that you acquiesce to the forgery and you could be on the hook as well.
Like everyone else said, though, you need to speak with a local attorney who practices family law.