Bottom Logan is based on the choice you make right after the Bandits attack Bareshade. You talk to him (and treat his wounds) and can either encourage him to attack the bandits at their camp, or convince him that he can do more good shoring up the town's defenses.
If you encourage him to attack the bandits, he gets captured, gang raped, and discovers how much he enjoys his prostate and spends most of his time after finding bigger and bigger cocks to sit on. That is Bottom Logan, and he is unavailable for relationships.