My dad has covid 19

So I’m really freaking out right now and need reassurance. This week my dad and my little sister both got a cold after moving me back into my dorm for the year on August 15th. And my dad just tested positive for covid 19 and he’s assuming my sister must have it too, but he doesn’t want to scare her so he’s not going to tell her he has it so that’s probably what she has too. I’m really scared and I don’t want to show it but I’m honestly panicking I want to cry. Neither of them have it really bad, they can breathe fine and my dad said he’s only got a stuffy nose but I’m so scared he’s 55 and my sister is 15 I don’t want anything to happen to them 😢 I’m so scared can it be worse than it appears? Have any of you had covid or know someone with it that’s doing better now? I saw an article about a boy who had covid but he had no symptoms and he was getting better, but when his parents went to check on him one day he was just dead in his bed. I can’t lose my dad and I can’t lose my sister I don’t know what I’d do. I’m only 20 I can’t lose half of my immediate family what will I do if something happens to them💔. My dad is the caring parent and he does everything for us please somebody help me feel better I’m freaking out😭