This is my theory.
Natural abilities in magick (natural/born witch) is half bloodline and half your spirit/soul's past. When we practice magick, we have a higher amount of energy running through us. I believe it only passes down from mother's to children, then daughters to their children. A witch or intuitive/sensitive doesn't stop being one while pregnant, and I feel that while the child is developing within their womb, it also experiences that energy and this effects the child's natural ability to sense energy and manipulate through thoughts/emotion (later in life) without any teaching or training. From the very beginning of consciousness within the womb, a child is experiencing first hand the feeling of the spirit world/high energy through their environment (their mother's body). If a fetus can recognize it's mother's voice, develop through the nutrition that it's mother eats, share a physical bind to its mother (the umbilical cord), why not the aura of his/her mother?