Kim Zolciak & Kroy Biermann Didn't Have Open Marriage, No Cheating Despite Rumors

There have been lots of theories thrown around as to what led to the downfall of Kim Zolciak's marriage to Kroy Biermann -- from rumors of cheating to claims the two had an open marriage ... but we're told all that noise is far from the truth.

Here's the deal -- the rumor mill has been going crazy since Kim filed for divorce from the former NFL star earlier this week ... with smoke online about possible affairs.

On the opposite end of that spectrum ... the anonymous gossip site DeuxMoi claimed the two had an open marriage.

However, sources with direct knowledge say that's all BS ... saying there was neither cheating nor any flexibility in the now-estranged couple's sex life.

Lots of 'RHOA' fans have also been wondering if Kim will be making her return to the show, or even if she’ll be a part of the upcoming cast of the spin-off "The Real Housewives Ultimate Girls Trip" amid her nasty divorce -- but sources say she has no interest in the reality TV game right now, and instead is focused on her kids.

TMZ broke the story, Kim pulled the plug on her 11-year marriage at the end of April ... saying it was "irretrievably broken with no hope of reconciliation." They've got 4 kids together, and she's asking for primary physical custody of them and joint legal custody. Kroy wants sole custody -- thus, the battle.