Do you think anxiety is genetic or comes from your environment? What are your thoughts?

I have 3 kids.  24. 17. 15.  My 17 yr old has become super defiant.  He and his 15 yr old sister have on their own decision stopped going to their dads because he and his household is so toxic.My 15 yr old and myself feel like we have to tip toe around my son who is 17. And physically towers over us and out weighs us. He has become emotionally abusive and on the verge of becoming physically...