I have a situation where a couple (shown as married with a marriage date) have two children. Using the husband's profile, the children are displayed. Using the wife's profile the children are NOT displayed. So I linked the two children using the mother's profile with existing family member process. This worked except it removed them from the father's profile. Looking at the children's edit screens, both the parents are shown in the appropriate area.
I have found in the past, that I have entered Chidren in only one of the Parents. and this has caused an anomoly.
Worth checking
All the best
Les
Regarding the same SEX. I find that this is the only way to enter them, by giving one of them the incorrect Gender.
As I have put many times on FORUM although it is an argumentive point, it temporarily solves it..
Regards
Les