We are learning about related facts or fact families in our classroom. To help students understand, I use this little story.
I tell them to think about a brother and a sister equaling a mom or family. We talk about how the brother will always be the brother and the mother will always be the mom no matter what order you put them in. To demonstrate this, I have two students volunteer to help me. I try to always call the two same students to help the concept stick. (I try to call on two students who really need the visual to help them.) After students understand that concept, I, then, add numbers.
Later, when we start working on fact families in a paper pencil fashion, kids have some background knowledge to fall back on. This analogy has helped my students and me so much. Hope you give it a try.