According to sources close to the Fast and Furious star Paul Walker family learned the "Fast and Furious 7" producers will use his brothers voices to help fill out portions of Walker's movie dialogue. merging archival audio of Walker's voice with his brothers' voices to fill in some gaps in the movies.
Sources are told it will use both brothers, Caleb and Cody Walker, to get everything to match up. TMZ sources say the production team tested the voice of each brother and learned that certain words sound better coming from one brother, and different ones from the other so they will combine them to help make the dialogue work. 

Our sources say the men have already started working on production. I think this is a great idea to keep it in the family Better family then some random guy who sounds like him right?