Should I Date The New Lady?

Good morning aunt Amara. Please I need your advise on an issue that's bothering me. My ex and I dated for five years through school and when we went for service, she found a new person and called off the relationship. Though her parents were not in support and after service somehow we came back.
Two months later she called off the relationship again and went back to the guy. 
I later heard from her brother-in-law that she said she has been pretending to love me throughout the the five years in our relationship and that she knew she was going to leave eventually. Though her parents and family were not in support of her new relationship but they had to let her be since it's her choice. I also moved on with my life too. 
Now my ex's brother-in-law's sister and I have been talking for some time now and along the line we fell in love with each other. I am close to the family of my ex, as well as the family of my ex's brother-in-law. I'm at a cross road now and don't know what to do. Please I need your advice. Is it a good idea to establish a relationship with the new girl in question?  Thank you for taking your time to look into this issue.

She has moved on with her life and you have also moved on with your life, so I have no idea why you shouldn't date another lady who you are comfortable and in love with. 
That she knows your ex or that she's related to her brother-in-law doesn't mean that you cannot date her. 
Please go ahead and date her, there's no need for worries.