Well... You've got to clarify something. The rich usually had a sway in marriages, though I wouldn't say that they had ultimate control, although they probably did have final say as to who the lucky person was. They probably also tried to steer their child to who they thought the right person, but probably didn't say outright, "You're gonna' marry such-and-such... or else."
I would avoid saying that such arrangements were common in the middle class (I view two periods - the Edwardian and Victorian periods from the middle class point of view... not everything was gilding and cherubs.) Middle class marriages were probably scrutinized, but rarely arranged.
Anyways... just how I think it worked.
Oh... and probably "Very Young" means parents probably started dropping hints around 12 or 13, basically the early teens.