Most Likely
1. Miyeon
2. Minnie
3. Soojin
4. Soyeon
5. Yuqi
6. Shuhua
Least Likely
Miyeon & Minnie : These two are the oldest so I think they're more likely to have children first.
Soojin & Soyeon : These two might want children someday but for now they probably think they're to young and they want to focus on their careers.
Yuqi & Shuhua : Since these two are still babies themselves, I don't think that they'd like to have children already.