The Other Woman (1971)
http://hkmdb.com/db/movies/view.mhtml?i ... ay_set=eng
and
You, Me and Him (1970)
http://hkmdb.com/db/movies/view.mhtml?i ... ay_set=eng

aren't they the same or is it a pair that belongs together? (i doubt that)

According to the HKFA it is the same movie:

http://ipac.hkfa.lcsd.gov.hk/ipac20/ipa ... ex=FILMBRP

The Taiwanese movie database lists the movie two times - but with the same BIG 5 title:

http://app.atmovies.com.tw/star/star.cf ... s003069864

Strange.