"Congratulations major @khloekardashian!" Caitlyn wrote. "I love you so much! You are such a strong woman. And what an amazing mother."
A source recently told ET, "Khloe is so grateful to have been able to expand her family and is adjusting to being a mom of two." The source added that Khloe "has been with the baby for a little while now."
"The two aren’t together and Khloe will have the baby full time," the source shared, adding that "Khloe wants Tristan in both of the kids' lives as much as he wants to be."
Another source added, "Khloe and Tristan are not back together and have not spoken since December outside of co-parenting matters."
The decision to have another child together came before Khloe learned that Tristan was expecting another baby with Maralee Nichols in December, a rep for the Good American founder confirmed to ET at the time.
Meanwhile, one of ET's sources says that Khloe and Tristan "have long said they wanted True to have a sibling, and Khloe even told her family she’d do it without Tristan if she needed to."
Khloe eventually decided against doing it sans Tristan. As she and the pro athlete "were on good terms, they decided to move forward with surrogacy near the end of last year," the source said, adding that it was only after that decision was made that "Tristan was caught cheating."