Mr. Sedley is Amelia's father. He begins the novel as a prosperous merchant and investor but is financially ruined and bankrupted by the second invasion of Napoleon.
When he is still rich, Mr. Sedley seems like an indulgent and generous father and husband. He takes care of all the material needs of his wife and daughter and, as we find out, was responsible for the later business successes of Mr. Osborne. However, when his investment luck runs out, we see that what had seemed protective and paternal was actually sort of infantilizing. Rather than letting his family know that his business was taking a turn for the worse, Sedley waits until bankruptcy to suddenly confess the extent of the losses. Later, after selling Jos's annuity, he repeats this behavior. In an ironic twist, at the end of his life it is Sedley himself who again becomes an infant – he slowly sinks further and further into dementia and his daughter takes care of him.