Girls, good evening. Can you tell me who has babies at what age they'r…

Girls, good evening. Can you tell me who has babies at what age they're lying on their stomach, lifting their head and holding their elbows? We're 3 months old, we put him on his belly, but he doesn't want to, I help him, my sister says that a course of massage is needed, she says it's not normal that he still hasn't propped up with his elbows. Thank you for your answers.