Well, there is a way but its super complicated for some people so keep concentrated on the following
first of all go to edit town (pretty simple)
then create your new neighbors or use one you already created
then simply drag the newly made household to your neighbors house then merge them
(here comes the "keep concentrated part")
check if they are both living together
make that DOUBLE check
now make sure your still in edit town!
so go click on the household
click split household
then get rid of the old neighbors
give them a nice new home -optional-
or you could delete them or put them in the worst house ever MUHAHAHAHAHA
go check! maybe your household is not the active one!
Now! (drumroll) YOUR DONE!