How Jessica Simpson’s Kids Welcomed Their Little Sister (Exclusive)

Birdie's older brother and sister made signs to welcome the new member of their family!

Jessica Simpson’s new baby girl has arrived and, according to ET's insider, no one is more excited than her kiddos!

ET learned that Simpson's daughter Maxwell, 6, and son Ace, 5, were waiting at the hospital for their new sister to arrive. They even made signs while they were waiting that said "Welcome Birdie!" 

“They were so excited and couldn’t wait to meet her. Maxwell and Ace were the first ones to hold her after Jessica and Eric [Johnson, her husband],” a source close to Simpson tells ET. 

In fact, the insider adds that the kids didn’t want to leave at the end of the night on Tuesday, and couldn’t wait to get back to see their sister the next morning.

The songtress-turned-entrepreneur and her husband broke the news of Birdie’s arrival with a touching post on Instagram on Wednesday, featuring a black-and-white image of Maxwell holding her little sister’s hand.

“We are so happy and proud to announce the birth of our perfect daughter, Birdie Mae Johnson,” Simpson wrote alongside the image, adding that their new bundle of joy is 10 pounds, 13 ounces.

ET's source also shared that everyone at the hospital, including Jessica’s sister Ashlee Simpson and her husband, Evan Ross, Eric’s parents and Jessica’s parents, guessed the baby’s weight — and Jessica’s father, Joe Simpson, won!

In October, Simpson spoke with ET in NYC about her pregnancy and getting to share the exciting news with Maxwell and Ace.

"They're so excited, because they're only 14 months apart, so they didn't get to experience the excitement of each other," Simpson said. "But when I told them that we're having another baby, I know that they'll remember that for the rest of their lives."

The fashion designer went on to explain that her kids had begun asking all kinds of questions about her pregnancy and the birthing process, which has led to some wild family conversations.

"They are most excited about learning how to do the swaddle. Maxwell, my daughter, is just so happy that it's a girl," she said. "They ask me the craziest questions that I can't say on TV ... 'How does the baby come out?' 'Where does the milk come from, I don't understand!'"

"I'm a little bit too honest, and Eric's like, 'I don't think we need to give out all the information, Jessica," Simpson added jokingly. "So, I'm scaring my kids, I think."

The proud mother cleverly revealed the name she’d chosen for her third little bundle of joy at her baby shower in January — using a sign that said: “Birdie’s Nest.

"She just loved the name [Birdie] and thought it was so sweet," a source told ET of her decision.

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