2 sides to every story.. I too have been accused of not ringing my son on his birthday and ignoring him, but then again, the phone was pulled out of the wall and the present I sent went " missing"... my ex wife could say that I didn't want anything to do with him... I could say something completely different.
Not saying that this is the case here.. but each story has 2 sides and in a break up neither side is completely innocent and in the middle are the children who are affected most... more often than not, its the children who are used as weapons to hurt the other person.
As for family court.. ive been there at a cost of $24000... if you are trying to prove that your ex wife is an unworthy mother then you have no chance in hell unless there is documented proof of abuse etc... it also works the same way to prove an unworthy father... seeing as you have a 12yr old who was obviously brought up OK ( or you would have taken your ex to court before), then the court will assume that all was OK until the break up and sour grapes dictate the agenda now.. happens all the time.
Good luck with whatever comes up.. I hope the children come out of this well balanced.
But I agree with Cow... this is not really the place to air dirty laundry.. there are mens groups that are for this purpose, you may be better contacting one of them