If both you and your spouse have terrible eyesights and wear glasses, does that mean your children will inherit this bad gene?

Yes, that may be true to a certain extent. While genetics can be linked to myopia, other environmental factors such as excessive near work, bad posture and lighting conditions can also be attributed to exacerbate the progression of myopia. Here is an interesting article explaining myopia and genetics. http://www.independent.co.uk/news/science/scientific-breakthrough-in-study-of-the-genetics-of-myopia-8489016.html