"Yeah, he has [been giving me stick]," Marty said of the 20-year-old. "But he still does my washing at home. He knows where he stands."
That hierarchy was certainly followed by Chiefs coach Dave Rennie when selecting his first side after Cruden was lost for the season through injury, with McKenzie consigning his highly rated brother to the bench.
Rennie was impressed with the way McKenzie marshalled the Chiefs' attack in the 35-27 victory over the Force, though he stopped short of guaranteeing the Taranaki pivot a second straight start this weekend.
"I thought Marty was really strong," Rennie said. "He did what we expected him to do - he controlled things pretty well, he's got a good skillset, he kicked for goal very well.
"We'll evaluate things but Marty was good. He can take a lot of confidence from that."
McKenzie is perhaps seen as the safe pair of hands at No10, a man who will make few mistakes and allow the playmakers packing the rest of the backline to shine. He revealed the coaches' advice before the Force match was to merely play his natural game, trust his process and "not try to do too much".
And with victory over the 11th-placed Rebels essential if the Chiefs wish to keep pace with the table-topping Hurricanes - their next opponents after the bye week - it's a formula that may be repeated in Melbourne.
"There's a lot of competition for the 10 jumper, with my little brother and with [Andrew Horrell] there as well," McKenzie said. "It will be interesting.
"We'll get back into training this week and whoever puts their hand up to get that 10 jersey, I'm sure they'll do a good job."