While it may not be something that would generally be discussed or considered right, there's nothing legally that would stop two 14 year olds from having sex. Legality shouldn't even be part of this conversation.
Never heard of the term "teen mom"? Girls can get pregnant as soon as they start ovulating and that can happen any time between 10 and 14 years old. Plenty of reports of girls getting pregnant at 12 or 13 years old.