I don't think I would combind Dad-only single parent with Mom-only,
unless it was after-the-fact of seeing that (oddly) they were similar
on everything.
If you want to flatten some variables transparently, you can take
(say) COMPUTE Both= 10*var1 + var2 ... and recode the values
to create your two groups, or however many groups you want.
What does "secondary data" (without the variable) mean? - that
you are only dealing with summary data from some analysis?
[ If that is the case ....
Dis-aggregating data that are in aggregate form is something that
is wanted, for instance, from vote counts. Some proposals are crap.
I did not spend enough time with the best-regarded one to figure if
it really worked, and there wasn't (10 years ago) broad empirical
support for it. ]
--
Rich Ulrich