In my opinion, I wouldn’t say that, but rather than the disposition for it might be more open for people. For most of these things to occur, the right environmental activities have to go down, or else it is likely that it will never reveal itself. For example, my grandfather, my father, and I had diabetes in my family. The trait is pretty strong in the family, but only a few people actually retracted the syndrome connected to that genetic proclivity. However, only a few of us went through it’s expression in our bodies. This was due to some sort of series of traumas, the likes of which were uniquely experienced for us in a way that expressed that genetic trait. Diabetes is heavily stress-induced, and I had some bad stress around the time I was 9-10. I was diagnosed at 13, and diabetes is notorious for taking several years to develop before diagnosis.
So the traits might build, but it would still take some environmental exposure to magick as something real. Kids would be raised watching and experiencing rituals, hearing family magick legends, even participating in lighter rituals. With that environmental exposure, it would probably foster continuous expression down family lines. I also know, however, people with those histories, and yet they got nothing, and most of their family got nothing, because they did not follow in continuing the tradition, being pretty much spiritually cut off. So like anything, in order for the magick line to continue, they would have to practice and immerse in it. This is of course my theory, but I have seen it turn on and off, and have had people reawaken magic from a family line that hasn’t happened for 3 generations because they decided to follow a magic path.