By Heller McAlpin Correspondent Do you know what a guncle is? I didn’t before I read Steven Rowley’s heartwarming new novel. But my children’s beloved guncle – that is, gay uncle – sure did. Rowley hits the sweet spot between hilarity and heart in this endearing charmer about a famous sitcom star who becomes the reluctant, unconventional guardian of his niece and nephew for a summer. As he demonstrated in “Lily and the Octopus” (2016), his debut novel about an adored pet dachshund’s illness, and “The Editor” (2019), about a struggling young writer whose editor, none other than Jacqueline Kennedy Onassis, helps unlock his career and personal life, Rowley knows how to tug heartstrings. In “The Guncle,” he doesn’t just flirt with sentimentality, he invites it to move right in.