Hearing some stories from my sister, her MIL is convinced my sister and her husband knows the sex and are keeping it for themselves. My response, who cares if my sister and her husband know. It's their choice. I really think my sister is still team green and doesn't know. It must be hard being accused of lying while being team green.
ETA: I wouldn't be upset if my sister was keeping it to herself. I would think that she would be honest and tell people they know but really I don't care. She's team green in my book and I'm not going to think otherwise.