My son recently turned 18 12/07 and is accussed of raping my ex-sister-inlaws daughters what can I do?

My brother left his wife in aug.Her and her daughters especially 16yr telling school,church my son made her pregnant to be spitful.Then wrote my son a note and said she lied.Continually haring my family.Sister inlaw even said she was pregnant with my brothers baby and then lost it.Was a lie.Now school called DSS on the 14yr old daughter because brusies the 16yr old beats on her.My sister inlaw umed it was me or my mom and told Dss and Police my son d the 14yr old sometime earlier or last year.She went to have a test to see if shes still a virgin today.They waited until my son turned 18 and the week I was in the hospital having gastric byp surgery.This little girl lets dogs lick her privates and in her mouth.She puts barbies and other things in her privates and has been for years.My son is proudly an virgin and plans to be until marriage.They always act like the victims.I have given the police notes I have received saying they lie.The mother is crazy and hypitual liar.Help