Can siblings of different ages play together?
Yes. Brave and Bonkers is written for kids from 6 to 12 at the same table, so a six-year-old and an eleven-year-old play the same adventure with the same one-page hero sheets, and the grown-up running it goes round the table by seat so each of them gets a turn every round. Steer the youngest toward the heroes with the fewest choices, and if the oldest would rather, they can run the game for the others.
Which hero suits which kid
The rulebook sorts the seven heroes by how much there is to think about on a turn. Ash of Ironhold and Brick have the fewest moving parts and suit younger kids and first-timers. Zap, Lumi and Bard.exe carry the most decisions and suit older kids. Sneaky Sam and Whiskers sit in the middle.
The rulebook also says not to enforce it. A six-year-old who wants the wizard can have the wizard, with you beside them reading out the spells. If two of them want the same hero, print a second copy and give one of them a new name on the spot.
Keeping the youngest in the game
Sit the youngest next to you. For their first turn, walk them through it: the rulebook prints the five lines to say, from “It’s your turn” to “Say your catchphrase.” After a round or two most kids take their own turns, and the adding can stay with you for as long as they want it to.
A hero who runs out of hit points is Down until the fight ends or somebody heals them, and a Down hero can still Cheer: once a round, just before a friend rolls, they shout encouragement and the friend adds a four-sided die to the roll. So the youngest is still in the game on the turn their hero is flat on the floor.
Keeping the oldest interested
Give the oldest one of the busier heroes and the longer version of the adventure. Adventure 01 says a table of mostly ten- to twelve-year-olds should get the two-hour version, because the one-hour core can play a little safe for them, and the second and third adventures each have a two-hour version too.
A job helps as well. An older kid put in charge of remembering what the party came to do, or of reading out the younger one’s sheet, usually takes it seriously. How old does my kid need to be covers the rest of a mixed-age table.
When the oldest runs the game
The rulebook was written for one adult or older kid as the Game Master, and an older sibling running it for the younger ones is exactly that. The adventure prints the words to read aloud and the number to compare each roll against, so a kid who can read the boxed text can run the table.
Sit nearby the first time. The page written for kid Game Masters talks to them directly about the job.
If there are only two of them
Two siblings make a real table. The adventures are written for three to five heroes. Each kid can play one, or one of them can run a second hero alongside their first. Adventure 01 also lists a smaller first fight for younger kids or a small party. Playing with just one kid goes through running two heroes.