Prior to 1899, he and his brother Acrisius lived in a city back East. At some stage, the brothers ventured out to the West with each other.
Proetus has a rivalry with his brother as they compete to win over a woman named Helen, by demonstrating their manliness in various bizarre ways.
Events of Red Dead Redemption 2
In the first encounter, Proetus and his brother are seen quarreling outside of Worths General Store in Valentine. Proetus asks the player to help them prove their manliness to Helen, the girl that the two brothers are competing over. He suggests that the player could shoot bottles off the top of their heads, in an attempt to prove their braveness.
They head to the behind the Worths General Store and place large bottles atop their head, and the player successfully shoots the bottles. Then they suggest they use smaller bottles, and they put some smaller bottles on their heads, which the player shoots. As a result, the brothers come up with the idea to perform the previous action but while standing on one leg. They do so, and the bottles get shot off their head again. They next ask to try it while hopping and doing somersaults, but the protagonist denies their request, saying that he and Helen have had enough. Afterwards, Proetus pays the player for their services and proceeds to leave with Helen and Acrisius.
In the second encounter, Acrisius and Proetus are seen arguing again, and ask the player again to help them to prove their manliness. This time, they suggest the protagonist punches them in the face, which they do. After that, they ask him to punch them in the stomach, which also happens. Then, they request the player punches them in the groin; both of the twins receive a punch here, and both of the men are seen lying on the ground and groaning in pain as a result. Afterwards, the twins and Helen enter the Saints Hotel.
In the third encounter, they can be found around Cumberland Falls and are seen standing by a waterfall. They each get into a barrel and ask the player to push them over the waterfall. After being pushed, neither of them seem to appear and this causes Helen and the protagonist to worry about them. They eventually find the two twins alive, and are surprised they survived. Proetus and Acrisius then realize that they were being foolish and compliment each other. They come to the conclusion that Helen is the cause for their feud and promise never to let anything come between them ever again. The twins walk away together, ignoring Helen's pleas for them to come back to her.
- Proetus and Acrisius' sibling rivalry and their names are based off Greek Mythology (Bibliotheca of Pseudo-Apollodorus) .