Ethan is conceived and born on the island in sometime after the time traveling gang shows up between 1974 and 1977. At this time, women giving birth on the island was obviously not a problem. So what happened? This is the whole reason Juliet was recruited in the first place.
Speaking of Ethan, we know that he becomes Juliet’s love interest as an adult. At this time, Ethan is an Other. So, he was obviously not killed with the rest of the Dharma crew. Did he participate in helping to plot the overthrow? Were his own parents (Horace and Amy) victims or did they manage to leave the island before this transpired? If they were killed and if Ethan knew they would be or worse yet participated in the planning, then it would appear that Ben is, or was, not the only monster.