son and daughter in law fights

My son has been married since 3 years and has baby girl aged 1.9 years. My daughter in law never get to know with us and they get seperated after their daughters birth and been living on the first floor of our house since then. My son is in family business with me. We been facing issues since after their marriage can say after 7-8 months. As I am 67 years old now, I still go to our shop daily basis 9am to pm and my son goes around 1pm and come to home around 8:30, he is creating issues with the business now that I donot work in the shop and he is saying if am not working then he will not allow me to get paid or take money out of the shop, we are parting profit on 50-50 basis.I do work at shop but i cannot do labour work because of my age, as we have bike repaiing and spare parts shop. and on the otherhand my daughter in law fights with my wife every other day, and we are not even interfering in their lives as they been living seperatly from last 1.5 years. She also threaten some times