I don't know if it's wise to be out in the open with everyone you know until you feel established with poly and have something solid you can hold up in the light, rather than in an exploratory stage.
And yes, it's your brother's problem that he doesn't believe Romeo's okay with it when he is. But that shouldn't matter to you, does it?
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein