Amelia Critchely, aged 11, and Elijah Critchely, nine, will take their place at the front of the Pelsall Carnival procession along with other 'royalty'.
Elijah said: "Carnival day will be brilliant, I am really looking forward to it."
The Pelsall siblings will join rosebud Olivia Pringis, six, maid of honour Ashley-Eva Johnson, 16 and maid of honour Ellie Stacey, 20, with Carnival Queen Elise Brewer, 15, on the first float.
The carnival on Saturday, July 2, is the first to be held in three years after the last two were cancelled due to the pandemic.
Carnival committee secretary Ian Rhydderch said: "In all the carnivals over the years we have never had a brother and sister as pageboy and princess.
"They are wonderful and from Pelsall so it will be a really special day for those two and the rest of our Royal Family."
The committee had to pick winners from entrants across Pelsall and Walsall during a competition last week.
Mr Rhydderch said: "It is one of the hardest things we do as a committee because all the entrants deserve a place on the top float but we can only pick a few.
"We are full speed ahead for the carnival now because of what happened the last two years, July 2 will be a really special day, from the procession through the town to the carnival, it will be great to see everyone enjoying themselves again."