Like Squinge said you have to use the package lots in the game.
If you want to restore thier relations you can do that later in SimPE.
I did it and joined families of all three default hoods together in a new one.
Wrote down the relations of all sims, like family and good friends, then packaged the lot.
Then used SimPE to restore thier relations in the new hood.
Was a lot of work, but for me well worth it, and had no problems so far.
