Brothers Chase d'Arnaud, left, and Travis d'Arnaud will face one...

Brothers Chase d'Arnaud, left, and Travis d'Arnaud will face one another in the big leagues for the first time on Tuesday, Sept. 29, 2015. Credit: Getty Images / Drew Hallowell; Joseph D. Sullivan

They were just children then, two brothers sitting side-by-side, watching the players in Dodger blue streaking across a television screen in Southern California.

Even then, they often asked what if? What if they one day reached the big leagues? What if they played together? What if they opposed one another?

Any option would have suited Chase and Travis d'Arnaud, who will meet as rivals beginning in the series opener between the Mets and Phillies on Tuesday night.

"It's going to be real emotional for me and him and my mom and dad as well," Travis said.

Travis could be behind the plate for the Mets, putting down signs with hopes of fooling his big brother Chase, an infielder recently promoted by the Phillies. Their parents will be in attendance, loyalties split between the two teams.

"When we were 6 and 8, we were watching baseball, talking about how cool that would be if we played with each other or against each other in the big leagues," Travis said.

The two have crossed paths in the minors, and this will be their first encounter in the majors.

Chase, 28, was promoted by the Phillies on Sept. 14. He's had brief big-league stints in 2011, 2012 and 2014 with the Pirates. Travis, 26, broke in with the Mets in 2013.

By coincidence, the brothers will be staying at the same hotel, under the same roof, just as they were when they were boys dreaming of sharing the same big-league field.

Said Travis, "It's crazy that in a couple of days, it's finally coming true."