B.J. Upton, 25, plays center field for Tampa Bay, and Justin Upton, 22, plays right field for Arizona.
"It will be fun to get a chance to compete against each other, talk a little trash, stuff like that," Justin said.
Their father, Manny Upton, said Justin always followed wherever B.J. played and wanted to play, too.
"He was always tagging along and playing in games, even when he wasn't supposed to," Manny said. "This will be technically the first time they play with or against each other."
Rays manager Joe Maddon pointed out that a lot of brothers have played against each other or on the same team in the Major Leagues and that the parents are the real winners.
"I think it's very special for the parents," the Rays manager said. "I mean if I'm a parent, and I have two kids in the big leagues ...
"Watching it, it's just kind of curious. It happens more than you think. But when it happens to your group, it stands out a little bit more."
Manny and his wife, Yvonne, will head a large contingent of family members taking in the weekend series.
"I'm hoping both of them do well, and let the chips fall where they may," Manny said. "I want both of them to go 4-for-4 or 5-for-5, both of them hit home runs. Hopefully both of them play well, and whoever wins, wins."
Manny said Yvonne plans to make a fashion statement at the game that will declare her loyalties.
"She's got a little secret thing that's going to happen," Manny said. "She's going to have a jersey, I think, with both of them. She's going to have a DiamondRays shirt."
B.J. said he and Justin will likely see a lot of each other during the trip.
"He hasn't seen my little boy yet," said B.J., who became a father in May. "He's stayed here the last two offseasons. He knows how to get around."
Justin looks forward to seeing his older brother.
"I'll go over [to B.J.'s place in Tampa] and hang out," Justin said. "We don't get to see each other very often during the season, so I want to make sure I take advantage of the time."
During the season, their efforts to stay in touch often become a frustrating game of phone tag.
"I called him on the way to the ballpark [Tuesday], but they were on the field ... they were already on the field taking BP," Justin said. "I see he called me back, but now I'm getting ready for the game. That's what happens with the time difference problems."
B.J. acknowledged that playing against his kid brother in a Major League game will be a pretty cool occurrence.
"We know it's coming," B.J. said. "What we're more worried about is all the people who are coming down [from Virginia]. That's going to be kind of out of control. Not so much having to deal with them, but how many people you have to see, and you don't want to hurt feelings. It's going to be a hectic weekend."
Other than seeing a lot of family, B.J. said the brothers don't have anything special planned over the weekend.
"Our main job is to play baseball," B.J. said. "They'll come down here. We'll do as much as we can to please everybody. But obviously, not everybody's going to be happy, but we're going to try our best. Like I said, our main priority is to play baseball."
Both brothers want their respective teams to win, but they care about one another.
"He wants to see me do well and I want to see him do well," B.J. said. "That's about it."
Wanting the other brother to perform well won't alter the way either plays in the game, though.
"When I get out there I'll be trying to take hits from him and I'm sure he'll be trying to do the same to me," Justin said.
And, like Maddon said, the parents will be the true winners this weekend.
"They are probably more excited than we are and looking forward to it," Justin said. "I'm sure they never thought it would happen, and it's a dream come true for them."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.