Only a few minutes have elapsed in Luke Greenfield’s dual-language road-trip comedy “Half Brothers” before the mawkish meter hits the red. The movie never stops revving it.

Renato (Luis Gerardo Méndez as an adult), the head of an aviation company in Mexico, resents that his father, Flavio (Juan Pablo Espinosa), didn’t return after leaving to find work in the United States. But days before Renato’s wedding, he gets a call from his dad’s current wife (Ashley Poole). The old man is dying, and he wants his son to come to Chicago.

There, at the hospital, Renato learns that the ginger-haired doofus he’s just chewed out at a coffee shop is actually his half brother, Asher (Connor Del Rio). Flavio, a lover of elaborate games, sends the two of them on a southwesterly scavenger hunt that involves mystery items like a key, a pawnshop ticket and a combination safe. He promises that following his instructions will reveal everything. It’s as a cruel a prank for the audience as it is for them.

Not that there’s much to reveal. The trip is a transparent excuse to get the siblings to spend time together — to bond over a baby goat and to make gasoline from moonshine, which cannot possibly be more difficult to stomach than this film. Asher learns to stick up for himself; Renato adjusts his empathy deficit. The movie clearly intends to send a serious message about how draconian immigration policies tear families apart. But a hard-hitting drama would be preferable to this strenuously wacky bromance.

Half Brothers
Rated PG-13. Half bros will be half bros. In Spanish and English, with subtitles. Running time: 1 hour 36 minutes. In theaters. Please consult the guidelines outlined by the Centers for Disease Control and Prevention before watching movies inside theaters.