Siblings of children with Down syndrome (or other special needs) don’t typically see their brothers and sisters as disabled. They see them as brothers and sisters.
That’s not to say that it’s always easy for siblings.
Here are a few resources to help those relationships:
A Wish Came Clear, a community of parents, friends, siblings, and caregivers of people with disabilities who celebrate things that others overlook.
An article I wrote for Chicago Parents Magazine highlighting tips for balancing parenting between or typically developing kids, and children with special needs.