I Have a Question

Why do people ask others to be their mom, father, or siblings online? Sometimes they even ask if anyone wants to be their daughter or son. And it's not to be perverted, they ask their online friends or anyone willing to volunteer. Last year, on a social app, someone asked me to be their mom but I didn't know what that meant so I declined the offer. Does anyone know, or have a guess, on what that's about?