Exhibitus interview questions

I had three online interviews and an in person interview. I had a week to complete a project and present for the last online interview. And my in person interview they flew me to Atlanta to headquarters to meet some of the team and flew me back the same day.

I was texted by the hiring manager after I was referred to him by someone who saw my resume from my application for another job at the company. We scheduled a call the same day and later set up an in person interview. I was asked an illegal interview question (Do I have a family?) and he went on about how having a family impacts someone's tendency to stay or leave a role that they don't really like. At the end of the interview he said he was interested in me and that he would let me know if I would be moving forward or not. I reached out a few days later to get an update and he said that he was going to continue looking. I asked why and he said he wasn't convinced I wanted to work there long term. I respect him for telling me that, but I feel he used that illegal question to help him make that decision. I should not have answered it, nor should you.