Blended family

In a perfect world, color is blind, but our world is not perfect. My husband was married for 13 years and our of the marriage they bore 4 kids who are all biracial. When my husband and I conceive our child will not look like them. My 11 year old bonus child keeps pointing out that our child wouldn't look like them, which is a given but it bothers me so much because regardless I would want our child to be accepted by all of the kids even if they look different. Is anyone out there with a blended family with a similar dynamic? I could use some encouragement.