| Quote #1
We were seven—who now are one, (line 17)
The speaker used to have a large family, but now he's the only one left. Notice how the "one" that's left is even isolated in the poetic line: he's separated from the "seven" by the dash in the middle of the line.
| Quote #2
And we were three—yet, each alone; (line 49)
Now the speaker's large family has dwindled to three – yet they're isolated from each other because they're each chained to a separate pillar. Like in the previous example, they're isolated also by the dash in the middle of the line.
| Quote #3
We could not see each other's face (line 51)
Even though the three brothers share a dungeon cell, they can't even see each other's faces.