I would say that having parents in some kind of STEM field can be a huge advantage, all else being equal. This is all going to be anecdotal, but for what it's worth: I grew up in a rural town with no science/technology community to speak of, and it wasn't fun educationally. We had a fully functional chemistry lab in our high school that we didn't even use once. I tried to self-educate but the public library doesn't exactly carry textbooks, and no one knew what the heck I wanted when I asked. My mom meant well, but she couldn't really tell the difference between a pop-science book for teens and the sort of thing that would have furthered my education. When I got to college, I found maybe hald of my classmates in our (small, ~20 students) physics program had parents in engineering or chemistry, who helped them with homework and projects from the time they were a little kid. I suspect that the fraction of science students with parents in a similar field isn't exactly representative of the general population. Perhaps more importantly, these kids had a way better sense of how to navigate their way through the educational system than someone like me, the first university kid in my family.
I get that my experience was about a lot more than my parents: resources, community, etc. But it's hard for me to buy the idea that a couple of STEM parents isn't an advantage, all else being equal. I had to swallow a lot of jealousy when I first walked into my undergrad research advisor's office, plastered all over with pictures of his eight-year-old daughter holding her science fair prizewinning thermoelectric generator.