Variations on the phrase “hang the moon” are a recurring textual motif that informs how the Pearce children think about The Meaning of Family. This colloquial phrase means that you consider someone to be exceedingly good and wonderful. One of the only things that William remembers about their parents is that their mother thought this of her children.

The Pearce children search for new family by searching for someone who thinks they hung the moon. The children begin to believe that Mrs. Müller is destined to be their family and consider approaching her with the truth about their guardianship situation, but this is a risky decision to make, as they could lose their temporary shelter if Mrs. Müller refuses to take them in. William thinks that he will know that she is the mother they need if he gets evidence that she thinks they hung the moon. Shortly after this, the Pearce children overhear Mrs. Müller talking to Miss Carr, and they hear her say, “If [the children] wanted to, I’m certain they could hang the moon” (296). For the children, the utterance of this motif is confirmation that Mrs. Müller is their family.