Dr.Geru is Dr.Gero's twin brother, he is smarter than his brother. Even though he is much smarter than his brother, his creations are complete failures. A example would be British Vegeta. He managed to get the cells of Vegeta but he failed in creating a clone. He is more powerful than chocolate and he is above the candy status.
On the left, you can see Dr.Geru and on the right, is Dr.Gero, you can't tell them apart as they are twins and for some reason, wear the same exact clothes and look no different what-so-ever and Dr.Geru will be in DBAF.