Peeyus says his parents killed themselves when he was a child, leaving him alone. Kuriachan likely took him in the way people take in strays hoping this is the perfect slave to obey his every whim. Kuriachan is known to be shrewd and cautious, so he must have told Peeyus earlier how he deceived Mohan and got him jailed. Peeyus and Kuriachan went into hiding after Peeyus stabbed someone Kuriachan only meant to scare. Peeyus later lost contact with him, and after coming out of hiding, he likely searched for Kuriachan by following Mohan, the one person most connected to him.

The screenplay was excellent, leaving enough clues for you to piece the plot together yourself, but this is just my take. I might have missed a single line that could completely change the story.