My two sisters want to give our brother their share of the property. Can we register a single release deed for all of them, signed by both sisters? I’m hoping this would mean paying only one stamp duty instead of two separate ones for individual deeds.

Yes, you can register a single release deed for both sisters, as long as it clearly outlines each sister’s share being relinquished to your brother. This will likely allow for a single stamp duty payment, but it’s best to consult a legal professional to confirm the exact process and applicable stamp duty rates in your specific jurisdiction.