Strange, i've never had that occurred. Every time an girl in my family tree reaches the age of 15 or 16, i get an marriage proposal, and if i decline i will get a new one roughly a year later. But nobody of younger age has had married in my campaigns.

OT: A 14 year old guy i knew (was on the same school) made an 13 year girl pregnant, she had the baby, and they say it wasn't an accident (though i really doubt that..)