It seems that Lusa-Human hybrids aren't born with their own personality and they lack emotions. They have a tendency to wander in random directions in search of what they don't have. For Meme and Pipi, they were able to find themselves by empathising with Lacile laughs and cries, but Barbaros must have had a very different experience. His first connection with another human being must have been through negative feelings, and that shaped his own personality. It's a tragedy, really.