The funny thing is that Biblical morality showed that God's chosen ones, those paradigms of faith and virtue like King David had concubines and affairs and killed a husband to get the wife. Outrageous behaviour by modern standards. Most Bible characters has less than perfect marriages.
The example of the New World Society is also fraught. Russell (jellyfish man) married to enjoy a sexless union and Rutherford a married man appears to have lived with his "anointed" mistress. Knorr was against the principle of sex probably because he could not control it in others.
Anyway it's nobody else's business if I have a harem!