Much time has passed since this book was first written, and we have no copies of it prior to a relatively recent point. It is entirely within the realm of probability that the original text was altered, probably also that it was altered many times. Insertions of a word here or there, a bit of clarifying description, perhaps, or some missing bit of speech from tradition. Pretty soon, whole stories are being included as the books were transcribed from one holder to the next.
That we were introduced to Simon & Andrew, James & John, but then don’t see them again until this point seems to indicate that the Capernaum synagogue scene was inserted later, breaking up what had previously been a continuous scene. This could simply have been an artifact of how the scene was written, too, so this kind of textual analysis only goes so far.
So we’re in the house of brothers Simon & Andrew. A lack of patronymic indicates a missing father, and since Simon is married and his in-law lives with him, he had probably been the head of his house. Now, of course, Jesus is the head of Simon’s house, and he is welcomed into the domicile as an honored elder. James & John, now part of this new “family”, are also now living here in Capernaum.