And, oh, how their competitors wish that were the case.
Dana Kirk made sure the Bremerton natives will become the first sisters to swim on the same Olympic team next month, completing the sister act with a rousing victory in the women's 200-meter butterfly last night.
The younger Kirk demolished the field in 2:08.86, touching the wall in Lane 6 more than a second ahead of second-place finisher Kaitlin Sandeno.
And when the sisters had finished swimming for the night, when they spotted each other by the warm-up pool, they finally engaged in a giggly -- downright bloody -- celebration.
Tara skipped toward Little Sis, leaped into her arms and began jumping up and down. Being about three inches shorter, Tara also smacked her shoulder into Dana's chin, cutting her lip and drawing blood in the process.
Oh well. All in a day's work.
"She was really excited," Dana said with a laugh. "I was like, 'C'mon.'"Dana Kirk led most of yesterday's final by a full body length, although the finish was closer than she anticipated.
At the 100-meter mark, Kirk was under world record pace and believed she had the race won. She started getting nervous with 25 meters left, then poured in on the last 15.
"I said, 'I have to get to the wall, I have to get to the wall,'" she recalled. "I could see somebody moving up my left side. Maybe it didn't look like it, but in the water, everything looks a lot closer than it really is."
Close or not, it wasn't nearly as suspenseful as Tara's 100-meter breaststroke final Friday. Tara finished second -- four-hundredths of a second behind Amanda Beard and eleven-hundredths ahead of Puyallup's Megan Quann.
Tara didn't get take a victory lap around a sold-out Long Beach Swim Stadium -- as Dana did last night -- and wasn't officially added to the team until Saturday. But as of this morning, they can both call themselves Olympians.
"Isn't that great?" asked their mother, Margaret Kirk, after watching her daughters reach the Olympic dream that almost never began.
Although the sisters started swimming lessons when they were six months old, it was because their parents were worried they would fall into the water and drown.
Dana didn't start swimming competitively until she was 7, and Tara was a gymnast until age 10, when she broke her arm while dismounting off the high bar. She couldn't tumble in a cast, so she swam with Dana.
"(It was a) slow realization that came, and once it was there, it stuck," Dana said on making the Olympics together. "Over the last four years, going to Stanford together, having (coach Richard Quick) there going 'Believe, believe, believe.' We came here and we both knew we had really good shots."
Only until after Dana qualified yesterday did Tara bring up a few topics: being roommates in Athens, pre-Olympic plans, post-Olympic plans.
"Stuff I didn't want to talk to her about before tonight," Tara said. "So we wouldn't jinx anything."
They sisters will return to their new apartment in Menlo Park near Stanford -- where Dana will be a junior this fall and Tara will co-term, finishing her undergraduate degree in human biology while starting her master's work.
They will be each other's date at the July 14 ESPY Awards, where Tara is nominated in the Female Collegiate Athlete of the Year category.
Then it's off to the training camp at Stanford, where the entire U.S. team will gather in late July in preparation for Athens. s
Dana said she is "95 percent sure" the sisters will room together in Greece, because they know each others tendencies so well, different as they may be. Dana likes to play games before races; Tara needs absolute quiet.
In their hotel room last night, they probably met halfway.
While Dana is done with her Olympic Trials, Tara has the finals of the 200-meter butterfly tonight.
"I still have one race to go; I have 200 meters to swim fast," she said. "And then ...."
It will be time to celebrate; unrestrained, fully relaxed.
The two sisters -- who share an apartment, a school, a coach, and a fulfilled Olympic dream -- now also share a part of history.