Re: how to phrase this question
In real life in this particular question, you can also say something like "Are you the oldest? Youngest?" and the person won't answer "Yes" or "No."
They will give you the details.
"I have an older sister, and then a younger brother and two more sisters." Or "One older sister, and then three younger siblings than me."
Or maybe something like "I'm in the middle of the mob."
Or "I've got one brother who's only 14 months younger, and a whole parcel of older sisters who treated the two of us like their little living baby dolls."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.