It depends on what dialect you are speaking. Mei Mei is little sister in Mandarin Chinese.
i dont no
Just say it.
There are many styles of Chinese. See related link.dì mèi
Chinese is a bit more specific when it comes to people in our family. There are two ways to say sister in Chinese. Jie Jie (姊姊) means older sister while, if it is your younger sister it is mei mei (妹妹).
姐姐 [jiě jie]
Niece = female Nephew = male
You can say: Woo Xiang Gan Ni.
i will say the babys aunt
小妹妹= Little Sister 小=Little 妹妹= Sister Xiao Mae Mae (may may)