Okay, let me just start by saying that I grew up with not one, but two brothers, so my trust issues started pretty early on in life.
If you've ever had to deal with a brother (or multiple brothers, for that matter), then you know that you most definitely cannot trust them ever.
Okay, maybe it's a little different once they're older and theoretically more mature, but after years of being lied to and deceived, it's a little hard to take what they say at face value, even if that face now has a beard and a mortgage.