Kim Zolciak celebrates son's birthday amid bitter divorce... and claims kids heard ex having sex with new woman

Kim Zolciak took her focus from her bitter feud with her estranged husband Kroy Biermann in recent days to celebrate her oldest son KJ Biermann's 15th birthday.

The 48-year-old former Real Housewives Of Atlanta star gushed about how proud she was of her son and his athletic prowess in a sweet Instagram post.

And on Sunday, she returned to sing her middle son Kash's praises in another post after he was named Defensive Lineman of the Year by Born to Compete.

Zolciak focused on her older sons' accomplishments just two weeks after she claimed in her bitter custody case that her children had been able to hear her estranged ex-husband Biermann having sex with multiple partners.

In her post celebrating KJ's birthday, Zolciak shared a barrage of photos tracing his growth from her little boy into a high school football star.

'Happy Birthday to the most incredible son @kjbiermann I had no idea what was missing from my life until you arrived,' she began her caption.

'You changed me in ways I could never fully describe. ❤️ You taught me strength, compassion, patience, and what the mother-son bond truly means,' she continued. 'You are my heart walking outside of my body, and every day you amaze me.'

She praised him for giving her the 'biggest, best hugs,' and she said she was 'so proud of the young man you have become. 

'Your work ethic, dedication, discipline, and drive especially when it comes to football are truly admirable,' Zolciak gushed. 'Watching you pursue your goals with such determination inspires me. 

She went on to remind KJ that 'No matter how old you get, you will always be my baby, my greatest blessing, and one of my proudest accomplishments.

'I am grateful every day that I get to be your mom. I love you more than words could ever express,' Zolciak continued sweetly. 'I hope this year brings you happiness, success, and everything your heart desires.

'Happy Birthday, son. Keep chasing your dreams – I’ll always be cheering you on. ❤️ Love you all ways always, Mom,' she concluded.

Zolciak shared multiple family photos from over the years, including snaps with KJ's older sisters, Brielle, 29, and Ariana, 24, along with several photos that highlighted the striking resemblance he had to his younger brothers, Kash and 12-year-old Kane.

KJ posed with Kash in one photo that made them look like twins with their athletic builds and masses of red hair. 

Another photo that was taken at a family dinner also featured Kane, who looked nearly identical to his brothers and sported the same hairstyle, and to top it off, all three boys wore matching black polo shirts as they posed with Kane's twin sister, Kaia. 

Kim also highlighted KJ's success on the football field in a photo of herself and her son that showed him beaming while holding up a certificate for 'Athletic Excellence' from his high school. 

She wrapped an arm around him in a more dramatic photo as he posed with her on a football field in uniform.

In her post from Sunday, Zolciak beamed next to a towering Kash as he held up a poster noting that he had been named Defensive Lineman of the Year.

She also included photos of him in uniform in the locker room, as well as footage from the awards ceremony.

'I am so proud of you @kash_biermann “Defensive Lineman of the Year” for the second year in a row,' she wrote. 'What an incredible accomplishment.'

'Your love for the game, your motivation, the hard work you put in, and your determination never go unnoticed,' Zolciak continued. 'am so excited that you and @kjbiermann will be playing on the same team this year. It will be such a special experience, and I can’t wait to watch both of you grow, compete, and make memories together ❤️.'

' I am excited to see where this journey takes you and to watch you achieve all of your dreams,' she wrote. 

'No matter what, know that I love you more than words could ever describe and couldn’t be prouder to be your Mom,' she concluded, adding that Kash deserved 'every bit of this recognition.' 

The posts were a rare moment of harmony with her children amid her bruising court battle with her estranged husband over custody. 

Late last month, Zolciak slammed Biermann in a declaration in their ongoing case for allegedly being neglectful to their four minor children, including by allegedly engaging in sexual sessions with multiple partners within their earshot.

In legal documents filed on Wednesday in Cobb County Superior Court in Georgia, the former Real Housewives Of Atlanta star said her children have alerted her to multiple instances in which Biermann, 40, had allegedly shirked his parenting duties.

Biermann's bachelorhood has come under scrutiny after he was awarded custody last month, as Zolciak said in legal documents that the children have been privy to his romances 'with multiple women in recent months.'

Zolciak told the court in her filing that the children will not see their father 'for hours on end, but hear him engage in sexual acts with his girlfriend of the moment.'

The filing marks the latest chapter in the former couple's ongoing court case to determine with which parent their children – KJ, Kash and twins Kaia and Kane – will reside.

Zolciak and Biermann are parents to the four children, while Biermann adopted Zolciak's two older daughters – Brielle, 29, and Ariana, 24 – from a prior relationship.

In her court filing, Zolciak said that she had been 'constantly contacted by every one of the children' while they were with their father because their basic needs were not being met.

She claimed that she 'immediately ensures that the children have what they need' when they ask her 'for food because they are hungry, or medicine because they are sick.'

Her court filing added that Biermann, a one-time regular for the NFL's Atlanta Falcons, had subjected the children 'to frightening rage-fueled tirades.'

Zolciak claimed that a court-appointed guardian had repeatedly exhibited poor judgment in assessing how she and Biermann co-parent the children by routinely issuing decisions that favor their father.

'The children’s interests are not being protected,' Zolciak alleged.

She added that the court 'is the only one who can help these children, and ensure their best interests are put front and center.'

Zolciak added: 'Unfortunately, as of now, all other professionals have woefully failed these children.'

Her recent motion claimed that a woman who had been seeing her ex sent her new boyfriend Kyle Mowitz, 45, a text telling him that Biermann is 'abusive.'

The text said: 'I believe Kim ... and [Biermann's] abuse is unlike any I've ever witnessed.' 

The former reality TV couple parted ways in 2023, and had a series of breakups and reconciliations before splitting for good. 

In March, Biermann asked the court to grant him full custody of their minor children, and he accused his ex of 'blatant mismanagement of basic parenting responsibilities' in a court filing. 

He told the court that Zolciak's conduct 'would be practically unbelievable to anyone not familiar with the circumstances' – allegations that she denied. 

She said of her case: 'I refuse to be bullied or have lies twisted into a narrative about who I am. I will not stay silent; the truth is on my side, and it will come to light - no matter how hard anyone tries to bury it.

'These accusations are completely false and nothing more than a deliberate attempt by Kroy to defame my character. 

'I spent five weeks away working on two TV shows to support my family and make sure my children are cared for – something I will never apologize for.'