I need help in remembering a tv miniseries or tv movie

What I remember about it is that it is approximately a Victorian era movie or miniseries. The show aired anywhere from the late 70's to late 80's. In the show, it involves an older sister or single mother and two younger children who are taken in by a compassionate wealthy young gentleman, possibly an aristocrat. He tries to raise the children to be fit for his level of society, but the young man becomes resentful of him and ends up stabbing him in the leg when the young man reveals that he is now broke because of bad investments. I...