Author’s practical guidance
"You're the big one now"
Source named in the book: adjustment to a new sibling (Volling) · Gerber (RIE)
The sentence sounds like a compliment and functions as a bill.
Say this now
“I need two minutes to finish this, then I'm yours.”
A real reason with a real end. Age is not a reason; time is.
“You go to bed later because your body needs less sleep than his does. Not because you're big.”
The explicit denial matters. Without it, they will supply the age explanation themselves.
Do this
- Give the actual reason — time, sleep, safety, ability — never age alone.
- Keep the word big for things they gain, never for things they give up.
- Let them be little on request without commentary.
- Check your own sentences for a week; this one is usually a habit rather than a decision.
- Ask relatives to drop it too — it is the most common thing a guest says.
Avoid this
- "You're big, you can wait." — charges them for a birthday they did not ask for.
- "Big kids don't cry about that." — makes the feeling itself a failure of age.
- Using size or age as the reason for any rule.
If it repeats
If the child starts using it themselves — I'm big so I have to — the bill has been accepted. Say plainly that it was never true.
Why the book suggests this
The sentence sounds like a compliment and functions as a bill. It arrives at the moment the child is asked to wait, to give up, to tolerate — and it explains that the reason is their age. Age is not something they chose or can appeal.
There is also a quiet threat in it that adults do not hear. If being big is why you now get less, then being small was better, and the child has a clear route back — which is what a great deal of regression actually is.
Related prepared situations
What happened next?

From this collection
Same Words: Two Children
45 prepared situations in this family area.