Or it could be that Sunny is literally the Sunny part of his life. look at Octacon. Other than him being extremely smart what else has he got to live for... His life hasn't really been the best. His father committed suicide. His sister was murdered. 2 girls he loved died. He lost his best friend. His greatest creation became the worlds deadliest weapon. And he finally gets to be happy with as simple as a daughter that isn't even is, but he will treat as such.