Scrumhalf Jake Gordon's knee injury means the Lonergan brothers have the chance to become the first siblings to play for the Wallabies together in a decade.
The last siblings to don the green and gold together were Anthony and Sai Fainga'a at the 2011 Rugby World Cup.
Lachlan Lonergan was one of 12 ACT Brumbies named in Dave Rennie's 38-player squad on Sunday, with his brother and fellow Brumby Ryan left off the list.
However, Rennie revealed Gordon's knee injury, which he suffered in the NSW Waratahs' match against the Otago Highlanders last week, meant he would likely be out for the Wallabies' first Test against France on July 7.
That has triggered Ryan's entry into the camp as cover until the Waratahs' skipper returns.
The Brumbies had the most players named in the original squad, with 12 selected but Rennie said, with a laugh, it was not because the side's head coach Dan McKellar had taken on an assistant Wallabies coaching gig.
"We've looked very much based on form and picking complementary players to see what we got. Obviously the Brumbies have got a lot of good players, who have got experiences, number of guys who have played a lot of Test footy and some good kids coming through and a really good system there," he said.
"It's exciting for those guys and obviously the Lonergan family, you know, Lachie selected and Ryan coming in as cover for Jake Gordon for the first couple of weeks.
"We're hoping that Jake will be available for Test two but if not, you know, Ryan's had a really strong season as well and it will be good to get him in and learn a bit more about him."
Ryan may get to stick around the national side past the first Test, as Gordon will have a short recovery window with the Wallabies playing France three times in only 10 days.
The 38-player squad features 11 uncapped players.
Scott Sio has been brought back into the Australian side and is joined by fellow capped Wallabies, and teammates, Nic White, James Slipper, Allan Alaalatoa, Tom Wright, Tom Banks, Noah Lolesio and Rob Valetini.
Additionally Lachlan Lonergan, Len Ikitau, Darcy Swain and Andy Muirhead are all in the mix for their first Wallabies caps after being named also.
Lachlan Lonergan was first called up to the Wallabies in April for a camp, before he earned his first Super Rugby start for the Brumbies later that the month. Rennie said the decision to bring him in was never in doubt after his performance against the Highlanders.
"Anyone that watched the game on the weekend will see why we've been very interested in him," he said.
"His got a real presence in the game, whether it's carry tackle or post tackle, an excellent thrower, and he's developing as a scrummager.
"He's not the biggest hooker going around, but he'll get better and better with time and we think being within our camp we can grow that but he's got a real point of difference."
Wallabies squad 2021 France Series (caps, club, age):
- Allan Alaalatoa (43, Brumbies, 27)
- Tom Banks (11, Brumbies, 26)
- Angus Bell (3, NSW Waratahs, 20)
- Filipo Daugunu (5, Queensland Reds, 26)
- Pone Fa'amausili* (uncapped, Melbourne Rebels, 24)
- Lalakai Foketi* (uncapped, NSW Waratahs, 26)
- Jake Gordon (5, NSW Waratahs, 27)
- Reece Hodge (45, Melbourne Rebels, 26)
- Michael Hooper (c) (105, Verblitz/NSW Waratahs, 29)
- Len Ikitau* (uncapped, Brumbies, 22)
- Feleti Kaitu'u* (uncapped, Western Force, 26)
- Andrew Kellaway* (uncapped, Melbourne Rebels, 25)
- Marika Koroibete (34, Melbourne Rebels, 28)
- Rob Leota* (uncapped, Melbourne Rebels, 24)
- Noah Lolesio (2, Brumbies, 21)
- Lachlan Lonergan* (uncapped, Brumbies, 21)
- Tate McDermott (2, Queensland Reds, 22)
- Fraser McReight (1, Queensland Reds, 22)
- Andy Muirhead* (uncapped, Brumbies, 28)
- Isi Naisarani (8, Melbourne Rebels, 26)
- James O'Connor (55, Queensland Reds, 30)
- Brandon Paenga-Amosa (9, Queensland Reds, 25)
- Hunter Paisami (6, Queensland Reds, 23)
- Izaia Perese* (uncapped, NSW Waratahs, 24)
- Matt Philip (9 Tests, Pau/Melbourne Rebels, 27)
- Lukhan Salakaia-Loto (25, Queensland Reds, 24)
- Scott Sio (68, Brumbies, 29)
- James Slipper (100, Brumbies, 32)
- Darcy Swain* (uncapped, Brumbies, 23)
- Lachie Swinton (1, NSW Waratahs, 24)
- Sitaleki Timani (18, Western Force, 34)
- Matt To'omua (54, Melbourne Rebels, 31)
- Taniela Tupou (25, Queensland Reds, 25)
- Rob Valetini (4 Tests, Brumbies, 22)
- Michael Wells* (uncapped, Melbourne Rebels, 28)
- Nic White (37, Brumbies, 31)
- Harry Wilson (6, Queensland Reds, 21)
- Tom Wright (3, Brumbies, 23)
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