I've been watching their videos for a little over a year now. I read a lot of the Japanese comments and all of them use the terms 娘 daughter & either 赤ちゃん baby, or 息子 son. The parents never use their children's name in any of the videos. I've seen the girl's name mentioned just once by one of the parents in the comments of one of their earliest videos but none of the viewers ever call her that. I think the parents prefer to keep that private.