Kim Zolciak Alleges Kroy Biermann Had Sex While Kids Were Nearby

'Real Housewives of Atlanta' alum Kim Zolciak claims her estranged husband, Kroy Biermann, is physically abusing their kids and having sex so loud they can hear him ... TMZ has learned.

In bombshell court docs, filed by Kim and obtained by TMZ, she claims Kroy threw one of their sons over the couch during a heated argument at his home.

The 'RHOA' alum also claims Kroy's been having sex with multiple women in recent months, including with one woman who stayed at his home and vacationed with the kids. Kim claims the kids "have reported on multiple occasions not seeing [Kroy] for hours on end, but hearing him engage in sexual acts with his girlfriend of the moment."

Kim said the court-appointed guardian dismissed the incident, claiming the kid was sizeable for his age. The 'RHOA' star insists the kid is still a kid, regardless of their size.

She said two other kids expressed their wishes regarding their living situations, only to be branded liars by the guardian.

Kim claims the guardian was made aware of alleged mental, emotional, and physical abuse by Kroy, but says "no professionals have sounded an alarm because the abuse did not ‘leave marks.’”

She says she is "constantly contacted" by the kids while they are in Kroy’s care, asking for food because they are hungry or medicine because they are sick.

Kim said the guardian takes Kroy’s side and even recommended Kroy be awarded primary custody, which the court did.

She also claimed one of his gal pals sent her new boyfriend, Kyle Mowitz, a text reading, “I believe Kim. He is abusive. And his abuse is unlike any I’ve ever witnessed.” Kim submitted the alleged text as evidence in court.

A source familiar with the situation tells TMZ ... the allegations in the paperwork are the reason why Kim has remained silent about the divorce for so long.

As TMZ first reported ... Kroy claimed Kim had failed to attend the required court-ordered therapy sessions, which led to her custody being suspended temporarily.