Hi Jeri, the two studies I quoted, were from areas of the US where homosexual marriage has been legal for some time.
I have also read studies from Scandinavia, where the same rates of "open relationships" apply.

The American studies included civil unions, with a "primary partner" and several secondary partners. Of course some male homosexual relationships are monogamous, but the rates of "open relationships" amongst male homosexuals are massively higher than amongst heterosexual marriages and partnerships.

The last study which I linked to gave the rates as almost 50/50 "open" and monogamous amongst male homosexuals.