Well I think in japan 14 is the age of consent in japan, but usually parents still have to approve. This is why so many anime have 14 year old characters in them. I used to always wonder why anime used 14 year olds while if it were america we would use 17 or 18 year olds in high school till I found out about that fun fact. I mean Evangelion, Bleach, Gurren Lagann, FMA, one piece, naruto shippuden and lots of other shows based around characters being 14 years old. Sure you could say that is the "target demographic" but recent polls on anime and manga show that majority of the fans are in their early 20's to 30's for a shonen pool.
I wish they were introduced earlier I just kept going daww every time I saw them XD. I hear they are the source of a good bit of comedy in the novel/manga. And they are big fans of Shizuo and try and set up traps to kill their brother for him so he will like them and let them see his brother. 
This cosmic dance of bursting decadence and withheld permissions twists all our arms collectively, but if sweetness can win—and it can—then I'll still be here tomorrow to high-five you yesterday, my friend. Peace. —Royal Tart Toter.