"Today, paternity test results reveal that I fathered a child with Maralee Nichols," wrote the NBA star on his Instagram Story on Monday, Jan. 3.
Nichols filed a lawsuit against Thompson in California, saying he is the father of her newborn son. In court docs, Thompson has said they had sex on his birthday in March 2021 during a "hook up."
Now, Thompson says, "I take full responsibility for my actions. Now that paternity has been established I look forward to amicably raising our son. I sincerely apologize to everyone I've hurt or disappointed throughout this ordeal both publicly and privately."
He went on to specifically acknowledge the "heartache" of his ex, Kardashian, following their breakup last spring.
"Khloe, you don't deserve this," Thompson wrote. "You don't deserve the heartache and humiliation I have caused you. You don't deserve the way I have treated you over the years. My actions certainly have not lined up with the way I view you."
He added, "I have the utmost respect and love for you. Regardless of what you may think. Again, I am so incredibly sorry."
Kardashian and Thompson share 3-year-old daughter True, and he shares son Prince, 5, with ex Jordan Craig.
E! News has reached out to reps for Kardashian, Nichols and Thompson for comment following the paternity tests results.
"[Thompson] told me he was single and co-parenting. I would never have gotten involved with Tristan if I thought he was in a relationship," Nichols said in a statement to E! News last month. "I saw Tristan in March 2021 around his birthday. He told me he had wanted to see me."
She continued, "I agreed to meet him in Houston at a private party on March 12... Houston was one of many nights we spent together. Soon after his birthday weekend in Houston, Tristan invited me to visit him in Boston."
The basketball player said that "the only time that I had sexual intercourse" with Nichols last year was in March 2021 in Houston, Texas, per court filings obtained by E! News. "I specifically remember having sexual intercourse with [her] in March because it was my birthday," he said. "[She] and I attended a party together at a hotel in Houston. [She] had called me and wanted to be with me on my birthday."
He also shared, "Contrary to [Nichols'] many inferences in her declaration, we did not have a serious ongoing relationship," stating, "We saw each other sporadically between December 2020 and March 13, 2021 and did not have sexual intercourse in California during that time."
Nichols said in her statement to E! News that she isn't seeking "a romantic relationship" with Thompson. "My goal is to raise our son in a safe, healthy, loving and private environment," she said.
A source previously told E! News that Kardashian was "focused on co-parenting" amid the lawsuit.