How do you flirt with your brothers older friends?

As far as brothers are concerned the last thing they want to have is a sister interloping onto their turf and that's their friends. Your brother also wouldn't want to have to put up with hearing about you from his friends. It's sort of like knowing your parents had to have sex to have you, but the whole scene is an ugly one. The most mature way to do this is be around every so often without becoming a pest so that hopefully one of your brother's friends will notice you. You could take out cool drinks for them and then walk away. Guys notice girls more when they don't make a fuss and aren't hanging around all the time, but just make the odd appearance.