@Samicat
Regarding your strange situation, it sounds like it's all up to your nephew. He's the recipient of your brother's largesse. He's the one they're buying the condo for. Honestly, if things are going to change, your nephew is the best person to talk to them.

Nammu mentioned "empty nest syndrome." I don't know how far away these condos are from your brother's house, but I'm wondering if this is a misguided way for him to keep his son close to home. Canada's a big country, and if he leaves Vancouver...

No real easy answers. I hope a good resolution comes out of all of this!