Reporting Underage Marriage - Process

Hello All . A relative of mine is set to marry off his son . The boy is probably just 19/20 . The girl is 14/15 from what I heard . I have not seen the girl. My parents tried counselling them saying child marriage is wrong , but they are adamant . If I make a complaint to SWC , will they register a FIR , counsel them or what? Does anybody know what exactly happens in such cases. I wish to remain anonymous.