Prospective adoptive parents should be urged to consider sibling group placements, Action for Children says.
The call comes during National Adoption Week and follows research from the British Association for Adoption and Fostering which revealed that 42% of people would prefer to adopt a single child.
The campaign is backed by DJ and I'm a Celebrity star Toby Anstis, who was adopted with his twin sister Kate. "I can't imagine life without Kate," he says. "It's a special bond and understanding that has helped us come to terms with being adopted."
Susan Cotton, adoption manager for Action for Children, said that, although many adoptive parents were overwhelmed by the idea of taking on more than one child, their families could flourish with the right practical and emotional support.
"When siblings enter care together, and all the other family ties have been broken, it's so important that, where possible, we keep them together," she said.
About 4,000 children in the UK await adoption every year. Sibling groups, along with older children, disabled children and those with behavioural difficulties or developmental uncertainty, typically wait the longest to be placed.