Marriage is a common concept between humans and not something that is hidden. If the couple intended to form a relationship of marriage, then they are married even if they did not have a verbal contract between them, and the children then are considered as legitimate. If the couple were intending to have a physical relationship, i.e., sexual intercourse and emotional closeness, the relationship is not considered as marital relation, and the children are considered as out of wedlock.
If one knows that the death of the animal was a result of the slaughtering process, it is permissible to consume. Otherwise, it is not permissible to consume.