The brothers combined for a 169-run partnership for the fifth wicket, and both raised their centuries during the partnership to ensure Australia continued to dominate England on an oppressively hot day at the Sydney Cricket Ground.
Shaun scored 156 and Mitch, eight years his junior, made a sparkling 101. The Marsh brothers became the first Australian siblings to combine for a century partnership since Steve and Mark Waugh put on 197 in the fifth test at The Oval in 2001.
The Marsh brothers also emulated the Waugh twins, and the Chappell brothers Ian and Greg before them, by posting individual hundreds during a partnership.
"To be honest I didn't think I was going to play any part for Australia this summer, because of my injury and obviously because of selection, so it's been a pretty whirlwind month for both of us," Mitch Marsh said. "And we're both really happy to be here now and to be contributing to a winning Australian team."
Left off Cricket Australia's contract list for elite players last year, Shaun Marsh was dropped for the tour of Bangladesh in August before being a contentious pick for the Ashes series, his ninth recall to the test team since his debut in Sri Lanka in 2011.
But on Sunday, Shaun Marsh, who was on 98 overnight, underscored his latest revival by quickly notching his second century of the series with a cover drive for a boundary off the fifth ball of the day from spinner Moeen Ali.
The 34-year-old batsman celebrated his 212-ball hundred by holding both arms aloft toward his team mates before a long embrace with his brother.
"Six months ago I lost my contract and was left out of the test team and didn't know what the future held at this level," Shaun Marsh said. "I went away and wanted to just enjoy myself and when I did get picked again it was emotional.
"It's been a lot of fun over these last six weeks and to be part of an Ashes series has been very special."
The younger Marsh, who has also been in and out of the squad because of injuries and form, would also get to savor an Ashes hundred at the SCG when he reached the milestone just after the drinks break with a two off Tom Curran.
The 26-year-old roared with delight and, on returning for the second run, stopped mid-pitch to hug his brother, unaware the ball had not reached the boundary and was still in play.
Luckily for the brothers, they each scrambled to safety before coming back together to again celebrate the Mitch's second century of the series.
"That was my fault," said older brother Shaun. "I think emotions sort of got the better of me and I just wanted to give him a hug and I saw him starting to celebrate and sort of lost all concept of where the ball was and what was happening with the ball.
Mitch "sort of pushed me off and said you better get down the other end. Thankfully it all worked out and I was just really happy for him."
The 169-run partnership was finally ended the next delivery by Curran, who got the ball to veer back and bowl Mitch Marsh to end an entertaining 141-ball innings that contained 15 boundaries and two sixes.
Shaun Marsh was eventually run out, after facing 291 balls and hitting 18 boundaries, as Australia searched for quick runs ahead of declaring at 649-7 midway through the afternoon session. It was his second-highest test score after his 182 against the West Indies in Hobart in 2015.
First Published: January 7, 2018, 3:28 PM IST