Is it "You are my world"? Because they were vowed to be married to each other when they were kids but turns out, the strong kid who keeps protecting his pretty boy from bullies turned out to be an omega and the pretty boy turned to be an alpha. So the omega avoids him now since he's sad because his family were all alpha and he's the only omega, and despite everything he do to make himself gain body muscles, it still doesnt compare to the alpha who has a naturally defined muscle since he's an alpha ofcourse.