My brother and I went to my aunt's house to play. For four days, he didn't wear a coat every day, and sometimes he only wore underwear. Excuse me, why is this?

There is no reason for this. It must be because of the hot weather.

You should think this image is very bad, right? This is no problem. After all, it is at home. Most men sleep in summer and wear only a pair of underwear at home during the day. It is normal for many men to go out shirtless in summer. So there is no specific reason, just because the weather is hot, men want to go shirtless, and men can go shirtless, so this will happen.