Eleanor has four siblings: Ben, Maisie, and Mouse are her full siblings, and Richie, Jr. is her half-sibling, and her mom and Richie's only child. Ben is twelve, Maisie is nine, Mouse (real name Jeremiah) is five, and Richie is a baby, meaning he's probably around two. All of the siblings have reddish hair, although none as red as Eleanor's.
Eleanor describes all of them as "crazy"—Maisie, she says, "fights like a street person" (33.44), while Mouse, the "craziest of them all," always has "a hammer or a jackrabbit or something stuck in his back pocket, and he refuses to wear a shirt" (33.42). They are a motley little crew.
Ben, edging into life as a teenager, seems uneasy a lot of the time, and traumatized at other times. Eleanor often mentions how hard it will be for Ben to grow up under Richie's rules: At Christmastime, Richie forces Ben to move into the basement, saying he's "too old to share a room with girls and babies" (32.3). Richie puts a lone mattress down there, and Ben's absolutely terrified:
Ben was scared of mice and bats and spiders and anything that started moving when the lights went out. Richie had already yelled at him, twice, for trying to sleep at the top of the stairs. (32.4)
Ugh. Looks like Ben's next in line for Richie's wrath in some ways, right behind Eleanor.
Before Eleanor was kicked out, she was closer to her siblings and they all allied against Richie. But when she returns home, things have changed. They've all started calling Richie Dad, and they hardly welcome her at all:
When Eleanor walked in the house, it was like her siblings didn't recognize her. (4.3)
Although Eleanor often serves as their main support when Richie's shouting and abuse wakes them up in the middle of the night, they aren't very loyal to her, probably because of their fear of Richie—Eleanor points out, "They have very confused alliances" (32.21). Ultimately it's Eleanor's siblings, Maisie especially, who expose Eleanor and tell Richie about Park.