I don't understand all the sibling hate. Are all your relationships that bad?
If he gets a $50k "market discount" his siblings can get an extra $50k and it's even. No harm, no foul.
I have no hate for my siblings. But money does strange things to people. If it is legally spelled out and your parents & you are good with it, go for it. My parents did discuss it with my brothers and sisters and none of them were going to farm, so they were actually happy I was buying the homeplace