Remember “K-Pax”? Kevin Spacey played a guy from that planet. Earth was too bright so he wore dark sunglasses. “Martian Child” stars a little kid from Mars played by Bobby Coleman. He too guards his eyes and sensitive skin from sunlight. He wears a “holding-down belt” of old D batteries so he does not float off his present planet. At the orphanage Dennis, as earthlings call him, hides in a big Amazon.com box marked “Fragile.” Dennis has abandonment issues. He awaits kin from Mars, who sent him here on a mission, to come get him. Meanwhile, science-fiction author David (John Cusack, who wrote haunted house guides in “1408”) gets Dennis. Neither has a handle on the father and son thing, but at the end of this male weepie, we see a ballbusting, cutthroat publisher (Anjelica Huston) tearfully read David’s new manuscript about his adoption odyssey as a single dad. As her close-ups tell us, it is indeed sweetly touching. Thankfully, writers Seth E. Bass and Jonathan Tolins do not concoct a traumatic backstory of their darling little alien with a hint of autism and a tease of extraterrestiality. I liked “K-Pax” for playing with the possibility that the guy in the psych ward really was a spaceman, but that film faltered by detailing Spacey’s psychotrauma. Director Menno Meyjes handles the warm pro-family formula nicely. With Joan Cusack, Amanda Peet, Oliver Platt, Sophie Okonedo, Richard Schiff and Howard Hesseman. 108m. (Bill Stamets)