Inheiritance 

I think there should be 4 Inheiritance books because in the third Eragon gets married and  gets a new blue sword and then he finishes his training and him and Roran should save Katrina. Then Roran and Katrina also get married. Then Roran gets the yellow dragon egg and names him Katrinak. Then Eragon trains Roran and one day Roran's yellow enchanted sword slid and sliced his stomach open Eragon heals it as much as he could but it leaves a scar like Eragon had from Durza then they gather the dragons that give Roran "The gift of the dragons" Then Roran transformed into an elf. Roran and Eragon both had children then Saphira and Katrinak mated then there were 10 dragon eggs that were given to their children and those eggs had hatched then Eragon and Roran train them