I recently commented about the Lincolns being married by an Episcopal priest - even though Mary was Presbyterian - and the collar of the man resembles early photos that I have seen of such priests, so I am going to ask if it is of Rev. and Mrs. Dresser.
Excellent, Laurie! Yes, it is Reverend Charles Dresser and his wife Louisa W. Dresser. Reverend Dresser married the Lincolns in 1842. Then in 1844 the Lincolns bought their Springfield home from the Dressers.
The lady is wife, Frances Adeline; youngest is William (as RogerM said); the oldest is the one we usually don't hear about - Augustus; and the other is Frederick.
Hint #1: This is a little like the questions Michael sometimes asks in that it is a "connection" question. There is a "connection" between this man's name and a very small number of writers who mention the man's name for a specific reason in their Lincoln books/articles.