Gender is basically you're a boy or girl, and no one can dispute what you are, it's biology. However the stereotypes that go with it are something you can change. Not all girls want a doll for their birthday and not all boys want a model car, when I was little I had all the typical "girly" things but what I had wanted was a remote control car, does that make me less of a girl?
One could argues that evolution has made it that way, the fact that all women/girl are natural carers and have a fondness for pink, this could be because in caveman times that was a women role and that they lean towards the colour pink because that was the colour of the berries we used to gather. However a lot has changed since then and don't you think society should too?
For me personally, I am this way because of the people I am exposed to and education but also choice, I am allowed to choose something different and I am not told I have to be a certain way... However, that was not always the case, there was a time a very long time ago when my mum used to pick out my clothes and also my friend, and she would always gravitate towards pink frilly dresses and my friend would always be daughters of her friends. Like I said before, this was a very long time ago.
At a small age this is what you do, you rely on your parents to choose for you, but as you get older you are more influence by what you see on TV than what your parents want for you. The media has a role in this, because it is not only what type of people you are exposed to but also what type of media you're exposed to.
I grew up with 2 older brothers and 1 sister who left to go abroad for a year when I was young, so that may have slightly influenced the way I am, but education is also a major factor, as education has taught me that if you dress a certain way you are going to attract the wrong type of attention, so I don't dress that way but other girls do and then complain when they do get that attention. People like that are the type of people who have been exposed to certain thing and then certain things are left out- like the consequence of acting that way.
So in conclusion, gender stereotype more often than none come from: family, education and the media, but if you've had the right education you can decide not to be said way, and who knows, if enough people change, maybe we can change the stereotypes?