i was cooking in the kitchen while overheard YAYA was arguing with Lei. At first, I didn't pay much attention. But then i realized that Lei seemed to be unable to settle it, and i had to stop to listen.

....
Yaya: 丁丁也是我的儿子！
Lei: 丁丁是你的弟弟，是我和妈妈的儿子。
Yaya：不是，丁丁是我的弟弟，可是他也是我的儿子，他是全家的儿子。
Lei：丫丫，谁生的丁丁，他就是谁的儿子。所以他不是你的儿子。他是妈妈的儿子。
Yaya：那我也是妈妈生的，我也是妈妈的儿子？
Lei: ....??

It seems that Yaya is really confused. This reminded me of two stories happened ealier.

Yaya was pretending to call back China. She wanted me to coorporate.
Yaya: 喂，你是谁？
Me：我是大姨。你是谁呀？
Yaya：我是丫丫。 你的哥哥呢？
I was so confused at this point, because we don't have any brother in the family.
Me: 哪个哥哥？我没有哥哥呀。
Yaya: 瞅瞅哥哥呀。
Well, actually she was talking about my sister's son. Her brother.
Me: 瞅瞅呀，他不是我的哥哥呀。
Yaya：那你的弟弟呢？
It seemed that she really thinks that if she called someone something, everyone should call that person the same thing.

I was chatting with Yaya one day.
Me: 丫丫, 爸爸是我的什么？
Yaya: Husband.
Me: 那弟弟是我的什么？
Yaya:儿子。
Me:那你呢？
Yaya: 宝宝。