I don't understand
why you must implicate issues that are completely out of the
boundary... the boundary that marks your Love affair. Although it
can be quite hurting for people to insult, you knew very well that
his brother is firstly not only an outsider in whatsoever 'affair'
you deemed this as, but also knew nuts regarding anything at all.
Do you even have to take this insult personally and affect you
emotionally? I don't think it's necessary.
You rejected A - this is an action made and reinforced. Anything
that revolves around him... seriously, why do you EVEN have to
CONSIDER at all? If nothing goes into his thick skull, remember you
don't have to make him understand. It is not your duty
to.
This potential relationship with B - it depends on how you wish to
manoeuvre your direction. And this decision is made based on your
OWN feelings and thoughts... and NOT includes those thingy about A.
If Love overwhelms future obstacles which you have forecasted
(Going overseas and study), a relationship is possible.
P.S: When we were young, our parents bought us toys. We all know
that toys are something that would be dumped, donated or given away
when we become much older. Despite knowing this fact, toys were
STILL bought.
A relationship
doesn't always have to consider its length to be
meaningful. 
Cheers
