I don't know of any method of analysis of busts that would demonstrate a genetic connection between Caesar and Brutus. We will have to ask an art historian on how secure their IDs of these busts are, but even if there were such a method I don't think any of them are that secure. They don't come with names attached, and one method is to compare them to coinage which has busts and names in the same place. An aside: despite what Wikipedia says about Servilia appearing on a coin, the bust in question on that coin is actually Minerva.

Even if the IDs of the busts were to be secure and a method existed, I doubt anyone would undertake such a project. Caesar was only 15 when Brutus was born. Goldsworthy considers this young enough to discard the possibility out of hand despite the ancient rumors that Caesar was the father. Meier doesn't even address the issue. Those biographies I have at home and could check, but in addition I don't know of any scholar that takes the possibility of Caesar being Brutus' father seriously.