Its my sisters 30th birthday this weekend. As a gift I took her for a pamper session and lunch mid week. At the end of the day, she said "See you Saturday night then wink wink". I was bemused. She told me that BIL had organised a surprise birthday meal for her, but she had found out. She was mortified to discover I knew nothing about it. When I phoned BIL he said "Its friends only, no family". My sister was so embarrassed and I am so cross with him. I made him god father to my DS too.
She always defends him though which worries me. When they were planning their wedding she came round with the brochures of luxury foreign weddings, knowing that we were a family so she could see what we could afford. She phoned later that night and said "Sorry, BIL has decided no children, he doesn't want to get married with the sound of the kids club in the background".
It should worry you. He sounds like an arse. My sister is in a horrible relationship and it makes me that she defends her DH. He mentally and emotionally abuses her. He is trying to iscolate her from her family by annoying you. So in a way, but falling out with him, knowing she will back him up, you are kind of letting him win.