My elder brother passed away last year. Should I perform his Shradh on Dwitiya?

Yes, if he passed away on a Dwitiya Tithi, then Dwitiya Shradh is the primary day to perform his annual Shradh during Pitrupaksha. If he passed on a different tithi, perform his Shradh on that tithi’s corresponding Pitrupaksha day. However, many families also include recently departed close male relatives in the Dwitiya Shradh as this is the traditional day for honouring the fraternal lineage.