bloody New Zealanders get another brother combo. First Whitelock's now Savea's.. want to give us one?
From the 2000s in Australia...
Last ones to both play for Aus were the Kefus (number 8, inside centre). Post Kefus, the Tahs had the Edmonds (hooker and five eighth). Currently, there are the Lucases (five eighth at the Reds, scrumhalf at the Tahs), and the Timanis (Sita at lock, Lopeti and number 8). Morahans are still a possibility (wing/fullback Reds, outside centre Reds Academy), although time is probably up for the Tapuais. Oh, and earlier there was Tyrone and George Smith at the Brumbies.
I'm sure I'm forgetting a few, too. No doubt a couple of people will remind me.
If you want to be cheeky, you could refer to Ebersohn at the Force, although he's not Australian, he does have a brother playing Supe rugby.
If you want cross-code, there were the Kasopowiczes (one medium-fast bowler for Queensland and Australia, one blindside flanker for the Tahs).