Physical Description:
Jacob is quite short for his age, four feet, five inches. In turn he is rather strong, at least for a little boy.
He has darkish blonde hair, wich he wear slightly long, big brown eyes, and a tanned skin.

Mental Description:
He is a very independently thinking child, wich often gets Jacob into trouble, as most grown-ups can´t stand that trait on children. And, admitedly, his social skills with people his age aren´t much more remarkable.
But Jacob is very intelligent with lots of knowledge and a photographic memory, and if he wants to know something, no matter how copmlicated, he learns it. Jacob generally tends to get what he wants as he is exordinarily stubborn. And proud of it, to the everlasting despair of all adults.
He doesn´t know a lot about the magical world yet, his mother refusing to talk about it more than strictly necessary, but that will change soon...
As a result of more or less only having his family as confidants Jacob is quite a bit self-conscious. He usually hides that by witty (and often quite mean) comments.
Also he is very analytical, there is little he can´t find out if he wants to.

Biography:
Jacob Fox is a pureblood, but but his biological father, who was the only one in the family who cared about bloodstatus and things like that, took off years ago. Jacob´s mother didn´t like him terribly much, so soon afterwards, when Jacob was still a toddler, she married a muggle.
How the two, pureblood and muggle met, is actually a rather touching story.
After having abandoned the magical world, Jacob´s mother had nowhere to go and didn´t know a thing about the new world she chose. But when she sat on the street, craddling her little son, there was one man who helped her. Eventually pity became friendship, friendship became love and they married.
He is the man Jacob call his father, by the way.
The two have three little children together, it isn´t known yet if they are magical.
Jacob grew up in a loving family and is close to all of his relatives, but without any knowledge of his powers until a fateful day when he was six, Jacob first using magic then.
Jacob didn´t know before because his mother, despite being a pureblood, always thought the magical world to be archaic, backwards and therefore wanted to protect her family from it.
That is why Jacob has none of the prejudice many other purebloods have.
His childhood was mostly spent outside, his tanned skin being a witness of that, be it by reading in a park or lonesomely training boxing - someone as troublesome as Jacob would need skills like that someday.
Since Jacob grew up in a large city he isn´t used to particular quiteness, even though he would like to change that soon.

First Instance of Magic:
Jacob was six years old, it was his first day in primary school and dozens of muggles saw it. That is because it happened on the schoolyard in the break.
Jacob´s new classteacher had called him an insolent brat after he refused to apologise to another child for calling him an mindless idiot. In his defense, he had been insulting Jacob way before that.
And all of the sudden the teacher and the other child got a very red, very prominent rash on their faces.
He had no idea how that could have happened, until his mother told him of a world that exists paralel to the one allready known to him - The Wizarding World.