Make a family tree that includes both adoptive and birth children. This solidifies that it doesn't matter if one has different birth parents; he/she is still an important and loved member of your family.
We may have to pass on this one. We have an adoptive child, and no birth children. But I think it will be a fun idea when S is older to put together a family tree showing both her adoptive and birth family. We even have pictures of some of her birth family, and we're looking forward to sharing them with S so she can appreciate all the people who love her so much.