The news follows reports that 33-year-old Kardashian is "distraught" at the apparent revelation of infidelity.
It's the first time anyone close to Khloe has spoken out since the accusations that Tristan kissed another woman.
Kardashian has already begun to experience early contractions, TMZ reported, noting her mother Kris Jenner flew to OH to be with her Wednesday morning and that other family members will do the same this week.
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Stephanie furthermore shared messages allegedly from Mr Thompson - one of which says "I would pull ya hair and kiss you than rip ya clothes off".
Wednesday: The Kardashian's family have rushed to be by her side after the pregnant star started having early contractions on Wednesday. In fact, this is the second time Mr Thompson has been with other women whilst a partner is carrying his baby. Thompson was also caught on film having a rendezvous with another woman while at a club in NY and it's reported that this wasn't his only elicit tryst during Khloe's pregnancy.
The woman in the video was allegedly identified as Instagram model Lani Blair. The pair was then photographed on their way to Meatpacking private members club Soho House. She was also seen with him at his hotel overnight and through the next day Sunday. Simpson, who was also highly rumored at one point to be Khloe's biological father. He was texting and talking on the phone and she was obviously looking over his shoulder. He had been in New York City over the weekend after the Cavaliers played in Philadelphia Friday night and played the Knicks in New York on Monday.
At around 8pm that night, nearly 48 hours after the two were first seen kissing at a club downtown, Blair was seen leaving the hotel in the same outfit but also carrying a Louis Vuitton bag.