For our children, who are adopted, it is not so easy. They remember some of their family because they were not infants when they came to us, but some of those memories are painful, and we don't have photos of their ancestors.
We've made some changes to how we do our ancestor altar to accommodate that.
First, we did a family history project and did a lot of research about their biological family members. We found photos where we could and some stories. Then introduced them to our ancestors, their new family and told stories about them.
Then the kids drew pictures of the ancestors they remembers or felt connections with and we framed the ones they wanted to put on the altar.
Then, they asked if they could include photos from family that still is living. Even though they are not deceased, we felt that this was an okay thing to do. They are not in their lives and are not likely to be again anytime in the foreseeable future but it would be wonderful if the kids could have a place to talk to them.
We decorated the altar with skulls, battery operated candles, and pretty items. Then lit the candles.
Now, they can talk to their ancestors whenever they like and we can come thank their ancestors for the wonderful children who are now a part of our own family.