o-o They do? That's stereotypical of you to say.
A guy should respect a girl. Though it's understandable when girls do stupid things like coming into the gym and saying their not wearing underwear (while wearing short shorts. I can't stand her). And you're brother's just growing up and he pry thinks that you expect him to agree with you when you see that Boy A is totally hot. Uhm..no? I've seen this happen, trust me. Girls will notice when a girl is pretty. It usually turns into jealousy, but not always, girls are able to admit that another girl is pretty (unless of course they're like too competitive and vain). As for boys, I've mentioned that I think a cartoon boy is cute (like Seto Kaiba or Kadaj. Orlando Bloom, even, though he's real life), and the boy I would be talking to would think not. <-< Disagree with me or not, but some boys just don't think like that. ..I'm being stereotypical, bah.
Still though, don't expect the boy to agree with you when you say Boy A is hot or cute. -.-