Sounds like the confidence of Gemini worked on you, though.
Julia has two sisters!
Here's the reasoning:
1. *Julia's brothers have sisters*: Each of Julia's three brothers has two sisters. This means in total, her brothers have 3 brothers * 2 sisters/brother = 6 sisters.
2. *Those sisters are not additional*: However, it's important to remember that these sisters belong to Julia's brothers, not directly to Julia herself. Julia and her sisters are siblings, not counted among the sisters her brothers have.
3. *Therefore*: Julia has 2 sisters (herself and one other).
So, while Julia's brothers have a total of 6 sisters, only Julia and one other sister are Julia's own sisters.
Even if we err on the side of the step, take the half sister entirely out of the equation and only focus on the step relationship, one would have claimed 0 sisters and the other would have claimed 1. They were talking about each other and they were both telling their truth. But the answer is simultaneously 0 and 1.
It gets even more interesting because neither my kid nor their step sibling are cisgender. I don’t know what to call their step so just use their name and pronouns now. The step still won’t acknowledge they’re siblings and I respect that a lot.
When these smart young folks take over, the world will get really cool.
Edit - This was way more complicated to explain than I anticipated.
I think It’s only ambiguous to a machine. To a human, even in 2023, these are likely default assumptions for a question phrased as above, unless being overly pedantic or attempting to “get around” the puzzle.
If you ask a model - or a person - “what does 1+1 equal to?”, it is also ambiguous, since we haven’t defined what “+” means, did not specify that we are dealing with natural numbers rather than eg elements in Z//2Z which could be similarly denoted.