I was very worried that my W's brothers and sisters would be very anti me. One day I met one of my BIL friends who said they were all sitting around at home chilling and invited me to come through.
I said to myself soddit, turned the car round and went. Best thing I ever did. Totally normal. No antagonism. And I walked away with volunteered intel that I never knew. i.e. they all thought their sis wasn't right and had told her so! Go figure!