估计你搞错了一个概念

对于配偶的情形是指: 主申请人在485批准之前如和男朋友或女朋友结婚, 可以在485批准之前递交follow-join-in,让其配偶同时拿到绿卡. 但一旦485已经批了, 一切都晚了.

而对于子女根本不存在这个问题. 楼主的孩子在485批准之前就是他的孩子. 可惜他在此之前根本没有替孩子申请. 只要他在此之前申请了,there is a substantial advantage to having the dependent obtain the Green Card based upon the principal I-485 applicant's case. The alternative will to file a relative petition and then have to wait approximately 4 to 6 years just waiting for the priority date to become current!