...An auction was held on the social media platform for a 16-year-old girl in South Sudan
Just sayin', I'm pretty sure there's nobody in South Sudan who would consider a 16-year old girl to be a child.
True enough... by the local customs she’s a young adult already. 21 year old adulthood is an artifact of modern Western society.
Maybe this is okay as long as the husband swears to support her all his life.