Is it normal for a younger brother to send flowers to his older brother’s girlfriend?

It is not appropriate to send flowers between brothers. Because men don’t like this kind of thing between men, and men don’t like giving gifts between men. If brothers send flowers to each other, they will make others laugh. Flowers are generally women’s favorite things. So if you want to send flowers, it is best to send them to women. Men generally don't pay attention to these things. You can give it to me, I don't mind.