Chantal Tkachuk's rule still stands.
And it remains pretty straightforward — there will be no fighting.
"Absolutely still in place," Florida Panthers forward Matthew Tkachuk, the family's eldest son, said of the not-so-subtle directive.
"Set in stone," added Ottawa Senators captain Brady Tkachuk, 21 months his sibling's junior. "That rule will not be broken."
The Tkachuk brothers have played against each other plenty since Brady made his NHL debut in 2018.
There was that memorable first meeting where nearly 40 family members sported specially designed jerseys honoring the occasion.
The pair then met nine times during the NHL's pandemic-shortened 2020-21 season when Matthew's Calgary Flames and Brady's Senators suited up in the one-and-done North Division necessitated by COVID-19 travel restrictions.
But with older brother now in younger brother's Atlantic Division stomping ground with the Panthers following a summer trade from Calgary and subsequent contract extension — along with an Ottawa group looking to make a playoff push following a painful, protracted rebuild — the temperature of the sibling rivalry is set to be turned up.
"Really fun when we played against each other twice a year," said Matthew Tkachuk, 24, who will face Brady and the Senators as true division foes for the first time Saturday when Florida hosts Ottawa.
"But now the games, they matter a lot. Before they didn't matter as much."
Brady Tkachuk agreed there will be an adjustment to the new dynamic.
"Definitely gonna be weird," said the 23-year-old, who like his brother is signed long-term. "But we're both excited for it. It's not going to be all the spectacle that it used to be. There's going to be some big divisional games, and we're potentially going to play in the playoffs.
"Going to be stressful for the parents, especially my mom, but it's exciting."
St. Louis forward Robert Thomas lived with the Tkachuks' father, Keith, who played 18 NHL seasons, and Chantal Tkachuk during his first two professional campaigns.
Matthew and Brady were out of the house and in the league by then, but around during the spring of 2019 as the Blues marched to their first Stanley Cup.
"They love competing against each other," Thomas said. "I don't know what's gonna happen there. I don't know how Chantal is gonna maneuver that one.
"But it'll be pretty fun to watch."
Vegas Golden Knights captain Mark Stone, who took Brady under his wing in Ottawa before getting traded, will also tune in when the Tkachuks meet.
"It'll be fun to have those two playing," he said. "Two good teams in that division going forward."
There's no doubt the Tkachuks — they also have a younger sister, Taryn — support each other when not going nose-to-nose on the ice.
Brady made waves on social media in last spring's playoffs when he was in Calgary cheering on the Flames, usually with a couple beers in tow.
"Tons of the guys on the team had family there doing the same thing," Matthew Tkachuk said. "The difference is Brady just plays in the NHL, so he's a little more recognizable.
"I loved it."
New Jersey Devils center Jack Hughes has played against his brother Quinn, a star defenseman with the Vancouver Canucks, in the NHL.
"First few shifts, you're kind of laughing about it," Jack Hughes said of sibling games. "(The Tkachuks) are different than me and Quinn. They're pretty in-your-face. I wouldn't be surprised if something weird happened between those two."
"I was asking someone if we're gonna see a Tkachuk fight this year," Quinn Hughes said.
"I hope not, but you never know."
Dallas Stars goaltender Jake Oettinger, who played with Brady Tkachuk at Boston University and the 2018 world junior hockey championship for the U.S., also isn't convinced the "no fighting" decree can withstand the individual desire to eventually grasp hockey's ultimate prize.
"That's the best part about those two," Oettinger said. "They're brothers and best friends and close, but once the puck drops … I'm sure those guys will fight at some point in their careers.
"They're two of the best players in the league. It's gonna be exciting."
The Tkachuks, however, are adamant about potential fisticuffs.
"The games will matter a lot more," Matthew said. "We'll ramp it up a bit. But at the end of the day, he's still my brother."
"We're gonna be having competitive games," Brady said. "Just who we are as people, players. We both want to win … expect more battles.
"But never cross the line."
Otherwise, they'll have mom to answer to.