The Fall of the House of Usher.
Question: How does The Fall of The House of Usher connect to other things we have read or discussed?

The Fall of the House of Usher is a short story by Edgar Allen Poe. It connects to the short story Rip Van Winkle by Washington Irving, as well as to another work by Poe- The Raven. Rip Van Winkle is a whimsical American fairy tale about a man who goes into the forest, meets some strange men, drinks an odd brew, falls asleep, and wakes up twenty years later. The tale of Rip Van Winkle has many illogical, unrealistic elements within it that aren't explained by the author- they are just elements that one has to accept. These elemants include Rip Van Winkle hearing his name being called, even though no one is calling it, odd looking men who do not speak, Rip Van Winkle's ability to survive sleeping for twenty years without any food or drink, and a dog that is over twenty years old. The Fall of the House of Usher also has many elements that are similarily unexplainable. For example, the dismal feeling that the narrator gets when he looks at the house, the narrator's ability to hear the sounds he is reading about, and a blood-red moon that appears suddenly out of nowhere. These elements are in opposition to the enlightenment- which is a movement we discussed in class. The enlightenment was all about man being able to reason through anything, and be able to explain everything. The unexplained elements found within Rip Van Winkle and The Fall of the House of Usher argue against man's ability to understand everything, claiming that there are some things that man isn't able to comprehend.
The Raven also connects with The Fall of the House of  Usher. Both were written by Edgar Allen Poe, but that isn't the only thing that connects them. Both deal with internal struggle or strife. In The Raven the narrator is mourning the loss of his beloved, this causes him to read to far into the raven's message of "Nevermore". The narrator's imagination also plays a part in this, as well as in his fear of the tapping at his chamber door. Meanwhile, in The Fall of the House of Usher, the internal struggle is found within Roderick Usher, who becomes terminally depressed in light of his twin sister's illness. His internal struggle is so intense that he becomes physically ill. His condition worsens after he prematuraly buries his sister in the family tomb before she even dies. This element of internal strife has to do with Romantisism- which focuses on the personal strife of an individual, rather then on the strife of a greater community or humanity in general.

Question:
On page 690 of The Fall of the House of Usher the first paragraph talks about the pecularities of the Usher Family. "I had learned, too, the very remarkable fact, that the stem of the Usher race, all time-honored as it was, had put forth, at no period, any enduring branch; in other words that the entire famly lay in the direct line of descent, and had always, with very trifling and very temporary variation, so lain."
What exactly is meant by this?
Does this mean that the family only ever had one child, or does it mean that the other offspring were never married?
If it is that the family only ever had one child, does this have anything to do with the decay of the House of Usher occuring in this particular generation- given that there was a set of twins born as opposed to a single child?