Chrissy Teigen and John Legend have welcomed a son via surrogate, just five months after Teigen gave birth to their daughter Esti.

The surprise announcement came in a moving post on Teigen's verified Instagram page on Wednesday, in which she wrote, "Just minutes before midnight on June 19th, I got to witness the most beautiful woman, my friend, our surrogate, give birth amidst a bit of chaos, but with strength and pure joy and love."

Legend also shared a celebratory post to his verified Instagram, marking the birth of their "new love."

Teigen shared photos of their newborn son in her post and recounted the story of his birth, also referencing her family's joy over the birth of Esti while continuing to heal from experiencing pregnancy loss in 2020.

"For as long as I can remember, I've always wanted four children," Teigen's post began.

She continued to share that "after losing Jack, I didn't think I'd be able to carry any more babies on my own," going on to say that "during that time, ... one clear memory is being surrounded by people who wanted to make sure I wouldn't go through that pain and loss again."

Teigen wrote that in 2021, they began their journey to expand their family by way of a surrogate and had connected with an agency to inquire about "perhaps having 2 tandem surrogates, to each bring us a healthy baby boy or girl. Twins, kinda?!"

"At some point, early in our surrogacy journey, I came out of a therapy session, walked downstairs and said to John - I want to try to carry just one more time. If it doesn't work, we will be okay. We've already seen the worst," she said, adding that "I promised I would be okay no matter what happened. I remember saying I just couldn't go on wondering my whole life if I should have tried again."

Teigen wrote that she and Legend began the IVF process -- "the same process that gave us our beautiful Luna and Miles" -- which brought them their now five-month-old daughter Esti, born in January.

She explained that when they met their surrogate, named in Teigen's post as Alexandra, they felt she "was a perfect match for us the moment we spoke to her."

"As we crept toward the safe zone of my own pregnancy, we were overjoyed to learn Alexandra had become pregnant with a little boy. Our little boy," she said.

Teigen went on to give thanks to Alexandra and shared in her post that the couple chose to name their son Wren Alexander Stephens to be "forever connected" to their surrogate.

Legend and Teigen's newest addition joins siblings Luna, Miles and Esti. Teigen wrote an essay in 2020 about her experience with losing their son Jack.

"Our hearts, and our home, are officially full. And to our Jack, we know both their angel kisses are from you."