Mother starting lies

I guess I'm just wanting to vent and maybe look for some advice. I found out today that my mother and her boyfriend are going around telling people that me and my husband drugged my 11 year old brother and molested him when I kept him for 2 weeks about 4 months ago and she has even went as far as to also tell people that my husband's dad and step mother have touched my kids inappropriately which is not true all this has started because when I kept my brother he said that my mom's boyfriend has touched him so I took my kids to the Dr to have them checked out and while I was there the dr asked me what brought it up and I told her exactly what my brother had said and she called the social workers on my mom but they didn't do nothing because they questioned my brother Infront of my mom and her boyfriend and he's scared of them so he never told the truth