The daughter of actors Bruce Willis and Demi Moore, shared the news on Instagram in a joint post with her fiancé on Monday.
Commenting on the post, Tallulah's sister Rumer Willis, wrote, "The most beautiful love to witness and watch grow. I love you both so much. Justin I'm so lucky I get to call you my brother. Baby Lula my gift my queen my heart is so full. Obsessed with you both."