Sixteen years later, with Nico having ascended to the top of world freeskiing, the siblings stood arm in arm as New Zealand's second Winter Olympic gold medal was confirmed.
The younger Porteous today won the men's freeski halfpipe final at the Beijing Games and was able to enjoy the triumph with his older brother, who had finished 11th.
Nico was sore, cold and nearly speechless after the victory ceremony, overcome by emotion and also bruised by a heavy crash on his final run in difficult conditions at Genting Snow Park.
But even more than the gold medal, Porteous knew there would be one prevailing memory from the high point of a prodigious young career.
"I don't think words can really describe that," Porteous told Sky Sport about sharing the moment with Miguel. "I think that's something that me and him will cherish for the rest of our lives.
"Being able to come down and give him a hug at the bottom and have him right there by my side the whole time, isn't that anyone's dream, to have your family right there next to you in one of your most proud moments?"
They have been able to lean on each other through last four years, first when Nico battled the mental obstacles brought by his rapid rise, then during the Covid restrictions that kept them from home in Wānaka.
Coach Tommy Pyatt proved another vital component in overcoming those challenges, and Porteous said of his mentor: "I think that's the first time we've both shed a tear at the bottom.
"After everything, there's been so much stress on all of us away from our families and friends, it just really pays it off. He's such a legend, he's stuck by my side the whole time."
That same persistence was evident in Porteous' victorious run in today's final, the first of three and one that earned an unbeatable score of 93.00.
It was similar to the run that reaped X Games gold a month ago and Porteous knew he could rely on the familiar even as the wind increased the difficulty of already complex tricks.
"I just had one plan and that was to ski clean and smooth," he said. "It was really slow in there today so I had to be really on point and make sure everything was good. I just stuck to what I knew and it paid off."
That pay off, a gold medal to sit alongside the bronze he won in the same event four years ago, will take some adjusting to.
"I actually can't believe it," Porteous said. "It's been so heavy on my mind for the past three months.
"I'm really lost for words, it's such a whirlwind. I'm so cold, I'm pretty sore, but I really can't believe it."
