Perspectives about adult sibling relationships: A dyadic analysis of siblings with and without intellectual and developmental disabilities.

Rossetti et al. (2020) talked with adult brothers and sisters in pairs. One sibling in each pair had autism, Down syndrome, or another intellectual disability.

The researchers asked both siblings how they felt about their relationship today. They wanted to see if the diagnosis changed the warmth and give-and-take between them.

Pairs that included Down syndrome rated their bond as more mutual. They stayed in touch more often and shared activities.

Pairs that included autism felt less balance. The typical sibling often gave more help than they got back.

Plant et al. (2007) and Cohn et al. (2007) saw the same pattern earlier. Their large surveys also found Down-syndrome siblings felt closer and more hopeful than autism siblings.

Heald et al. (2020) looks like a contradiction at first. That survey says any intellectual or developmental disability hurts the typical sibling’s attitude and mental health. The key difference is comparison group: the 2020 survey compared siblings to families with no disability, while Zachary compared Down syndrome directly to autism.

Milevsky et al. (2022) and Abney et al. (2026) add nuance. Their interviews show all disability siblings feel both growth and stress. Zachary’s work sharpens the picture by naming which diagnosis leads to more balanced give-and-take.

When you plan sibling support groups or future-care talks, match the plan to the diagnosis. Families around Down syndrome may already enjoy shared activities you can build on. Families around autism may first need help creating moments where the disabled brother or sister can give something back, even small, so the typical sibling feels the relationship goes both ways.