Buying duplex with family member

Purely hypothetical, my partner i arent going to be selling any time soon, but this is an idea I wasnt sure would work. Based in NSW.

My partner and I bought our house in 2022 and used FHOG. So we are aware we are not eligible for any grants and will have to pay stamp duty.

My brother has not owned property before, and should be eligible for grants.

I was looking at buying land and having a duplex built. So we would own one and my brother the other. Is there a way to work this so he can still access grants? I know the loans would have to be separate for this to happen, but how would we go about something like this?