Not necessairly, yes they can become sick from stress and then die. Make sure his tank is warm, and moist. Make sure your feeding him on a schedule. Dont put alot of crickets in his cage because the crickets can stress him out too. Also i agree with the other post, tll your sister not to handle them that often. I usually handle my geckos 1-2 times a week. you can handle them daily but you have to make sure to wash your hands because its not good for their skin to be handled ALL the time. Also, put a towel (shirt, etc) over the cage, it makes them feel more safe and secure and will calm them down. Hope this helps.