I don't think you can leave out divorce for creating stepfamilies. On both sides
of my family there are instances of stepchildren and half-siblings due to divorce
and re-marriage. I grew up with the mindset that divorce was a very uncommon and
frowned upon thing in the Jewish community. Of course my evidence is only
anecdotal based on my own family, but I think divorce was probably more common and
possibly even more accepted than what I was raised to believe.
Fort Collins, CO