The "parent-child" relationship can have only one parent source (thus it's called the Primary Data Source) and all the rest of the data sources have to be secondary sources.
So you can't go from Source 1 to source 2, and then expect to go from source 2 to source 3 in the same sheet.
However, you can go from Source 2 to Source 1, and also go from Source 2 to Source 3 within the same sheet. Make Source 2 primary and Sources 1 and 3 secondary.
So it's not as relational as pure SQL would let you do.
Whether or not your data shaping will work for your specific example is hard to say given the limited info so far.