Khloé Kardashian Believed Tristan Thompson 'Would Change' Before He Allegedly Fathered 3rd Child

Tristan Thompson allegedly welcomed his third child with a woman he admits to sleeping with in March — when a source says he was still dating Khloé Kardashian

On the heels of the news that Tristan Thompson allegedly fathered a child with a woman he cheated on Khloé Kardashian with, a source tells PEOPLE that the Good American mogul previously "believed that he would change."

According to court documents obtained by PEOPLE, the woman, Maralee Nichols, is suing Thompson for child support and pregnancy-related fees after she said they conceived a child together in March. She gave birth to the baby boy last week, her rep told PEOPLE.

The Sacramento Kings player confessed to having sex with Nichols during at least one encounter, per the documents.

The source says Kardashian, 37, "knows about the baby" and confirms that she and Thompson, 30, were together in March. The former couple share daughter True, 3, and Thompson is also dad to 4-year-old son Prince, whom he shares with ex-girlfriend Jordan Craig.

Khloé Kardashian and Tristan Thompson. SHEIN X 100K Challenge 2021/Getty; Jack Arent/NBAE via Getty

The insider says that Kardashian had friends encouraging her "over and over again" not to take Thompson back after his past cheating scandals, but ultimately remained with him "because she always believed that he would change" and wanted to keep the family intact for True.

"She is just a really great person and wants to see the positive in people," the source says, adding, "It's just a sad situation to her."

The source also said Thompson and Kardashian were "doing great" while quarantined together during the COVID-19 lockdown, but that Kardashian "knew things would change" as soon as he returned to the NBA.

"She was just hopeful that he would stay faithful and loyal to her," says the source.

Khloé Kardashian and Tristan Thompson with True. Tristan Thompson/Instagram

"Khloe's family always tried to support her," the insider adds. "They always treated Tristan well even after he broke Khloe's heart multiple times."

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Thompson and Kardashian have been on and off for several years. After briefly reconciling, Kardashian and Thompson split for a final time in June amid more cheating rumors. Another source previously told PEOPLE that the exes are continuing to "keep things friendly" for True's sake.