I actually think it's disgusting that some people (on this thread), would deny their child such a rare and unique, life-changing education because their other child wouldn't qualify/get the same opportunity.
That could cause huge resentment for the child denied the opportunity that they had earned in their own right.
I know someone (an excellent hospital Consultant), who sent one child to private school, the other to state grammar school. She made the decision based on her individual's children's needs. She's an amazing mother who meets her children's individual needs really well.
@ThatJadeDreamer you can't deny your son this opportunity.
Sometimes people get selected for various things in their life, would you deny your younger son something he's selected for, because your eldest child wasn't?
It's just silly, you must let your children take what amazing opportunities that are available to them. It's not right to deny a child something amazing because the other child won't get it. Life doesn't work like that. How do we know what opportunities will arise for the youngest in the future?
Imagine your son finding out he missed out an this potentially life-changing opportunity because of his brother.
More importantly though, what does your eldest son want? As long as he's free to make up his own mind and not be guilt-tripped into turning it down, let him choose.