Should I feel bad?

Ok so my little brother (18) is visiting for the summer. All summer he's gone between our house my sister's house and my mom's. Today he comes in from my mom's house (about an hour ago) and we're talking like normal and laughing and then he randomly asks if taste buds can die. I said I'm not sure and if they do they probably regenerate why? He says he hasn't been able to taste anything all day and he's had a stuffy nose. About a week ago I know he had gone out with my sister and I told him even when you're out maintain a safe distance from people keep your mask on and sanitize. I've told him if he won't be safe he can't come here. Even though he's been sleeping at my house he spends most of his time with my mom and sister. I told him that a lack of taste is one of the major signs of covid and he needs to get a test and he flat out refused. I told him that it's not just about him god forbid he actually has it he may have a mild reaction but it could be worse for people around him and he still refused. I told him he can't stay at my house I have an asthmatic son who almost never goes outside now and we have two other kids (5,3,9 months). He got mad and stormed out and it blows my mind that he is so selfish (not just because of this he's generally a dick) that he's willing to possibly put other people at risk because just because he doesn't want to take the test. Anyway he stormed out and apparently went to my sister's house where she has a 4 month old. Im not sure where it would be best for him to even quarantine at. My house? My mom's? I'm calling the kids doctor in the morning and we're going to get tested as a precaution since he's been around us all and I'm going to be ordering in groceries now for the next 14 days. My 5 year old was supposed to meet his kindergarten teacher in the morning (it's a requirement for the school but he's going digitally). My husband is a truck driver and he's gonna sleep on his truck for 2 weeks instead of coming home (he's usually home every Saturday). Are we overreacting? Should we take precaution now it just wait and see what happens with my brother? We've been on like a light lockdown since this all started only going to the grocery store wearing masks disinfecting no large crowds going for walks in the park but keeping distance. I'm not freaked out but I feel like all of us should take a test and quarantine just to be safe but am I overreacting? Was I wrong for telling him he can't stay here? I feel like an asshole but I also know I have to protect my kids.

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