worse morning sickness with boy?!

Ok so my sister-in-law insists that people have worse morning sickness with boys. She says this is a well known fact !! I’ve tried to explain to her that the old wives tale says girls = worse MS but she insists it’s boys! Anyone else heard of this theory?
((Of course I know morning sickness does not equal gender, I was just curious if this was a thing because it was the first I’ve heard of it))