Interesting. I had 2 girls, a boy, then another girl. All with pretty much the same age gaps & the same father, but he did do different jobs when the kids were conceived. DS was conceived while he did a much less physical job.

My dad & his 2 brothers all had a girl, then a boy. Dad followed with another girl, but the others only had 2.

Mum's family was also girl boy girl, same as she had. Dad did the same strenuous job the whole time.