You will need an immigration lawyer to handle your case.
First of all, it does not matter if you are innocent or not. From what you are writing, it sounds as if you were accused of a crime, failed to meet in court, were convicted in absentia and failed to lodge an appeal. You are now convicted and the deadline for an appeal has lapsed. There is nothing you can do about that now, if you failed to face the charges earlier.
You can apply for a family reunification visa even if there is an entry ban in effect against you, but it is of course not self-evident that the visa is granted. If a visa is granted, the entry ban will be reduced or suspended. On a case-by-case basis, your rights to sustain a family relationship will be judged against any risk you (seemingly) impose on the society if you are let back into Germany. IANAL: Working illegaly might not be a reason to uphold the entry ban, but document fraud is a severe crime in Germany. Honestly, you must expect your visa application to be refused and that you will need an immigration lawyer to lodge an appeal for you.
I say again: You will need an immigration lawyer to handle your case.