The characters in Dear Brutus are similar to those in other plays by Barrie.

Barrie sometimes finds heroes and heroines among the common people— butlers, charwomen, scullery maids, or starving artists—but in Dear Brutus he explores the strengths and weaknesses of the affluent with similar results. The theme of a second chance at life is raised in his other works, for example, The Little White Bird, The Admirable Crichton, and Mary Rose. The character of Mary Rose is often tied to that of the might-have-been daughter of Will Dearth in Dear Brutus in that both are "delightful creatures" who disappear before they ever grow up.