Wedding ceremony is good! When i look at my little villager, i will think "Who is this little boy/girl exact siblings?". Family Tree could be nice. And also, Parenting skill are not in "kissing" or "making babies" way. Teaching children or telling a stories are good skill for increasing parenting skills. It would be nice if a villager could only make babies with its spouse. Multiple marriage (polygamy) might be good in VV4, if you want a male villager to have baby with two or three villagers, but they can't make babies with non-spouse villager. Maybe it will be a tradition of Isola!