The connections between the two characters stem from their transformations into an insect. As a tick, Grenouille represents the belief that some people in society feed upon others by draining the life out of them, much as a tick does to its host that it attaches itself to. Others exist only for him to satisfy his obsession of aromas. Gregor's change is an escape from this duties to his family. His life as an insect mirrors his life before he changes because he never expresses his own needs. He feels he doesn't have the power to make himself better, but in the end, his father does. After Gregor's death, his father asserts his power over those living in his house, suggesting that Gregor's self-sacrificing presence had drained the power from those around him. The motivations of the two characters are different, but their effects on others are very similar.
Grenouille and Gregor are both isolated, but Grenouille's is self-imposed, and Gregor's isn't. The co-workers of Gregor resent him, mistakenly thinking he's rich and having lots of fun as a travelling salesman. Grenouille uses people for his own gratification in obsessively pursuing their aromas, the essence of their souls. Gregor totally loses his ability to communicate, so his alienation becomes worse. Gregor's job provides him with no satisfaction, but Grenouille sees his work as his reason for living. Their deaths in the end are a relief to others.