"Thanks for giving me a million reasons to smile everyday!" the 'Bachelor' alum wrote on Instagram Thursday

Nick Viall showed his pregnant fiancée Natalie Joy some birthday love on Thursday.

As Joy turned 25, the former Bachelor wished his “greatest love, my future wife, and mother to my child” a happy birthday on Instagram.

“Every time I look at you I’m reminded how lucky I feel to have you in my life,” Viall, 42, captioned a carousel of Instagram photos Thursday. “Your spirit brings a smile to anyone you encounter. Thanks for giving me a million reasons to smile everyday! I love you Chicken.”

Joy commented on the post, “the best part of me is you 😭😭😭 i love you forever my chicken.”

Related: Nick Viall and Pregnant Fiancée Natalie Joy Look Forward to Making Baby 'Feel Loved' (Exclusive)

Earlier this month, Viall and Joy announced that they’re expecting their first child.

“Our biggest dream came true,” the couple wrote Aug. 8 on Instagram.

Joy explained to PEOPLE how she shared the news with Viall.

"I took two positive pregnancy tests, got a couple of baby outfits, and put them in a drawer, knowing Nick would open it when we were making dinner," she said. "He was shocked, to say the least."

Related: Nick Viall Reveals He Lied to His Friends About Sex of Baby on the Way with Fiancée Natalie Joy

Viall said he and Joy have been discussing how they want to raise their child.

"We have both always been excited about becoming parents someday, and we are so excited to be on this journey together," he added.

Viall and Joy got engaged in January when the Viall Files podcast host popped the question with a Brilliant Earth 18K yellow gold ring set with a 5-carat elongated cushion cut diamond. The pair celebrated three years together in July.

“I love our family we’ve started together can’t wait to see how it grows,” he wrote on Instagram on July 11. “Thanks for 3 incredible years and for always fighting for us. Can’t wait for the rest of our lives together.”

Related: Nick Viall and Pregnant Natalie Joy Take a Stroll in L.A. After Revealing They’re Expecting a Baby

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For their anniversary, Joy declared on Instagram that she “couldn’t have dreamt up a better man” than Viall.

“Thank you for loving every piece of me,” she wrote. “You make me feel heard, seen, valued, cherished, beautiful, safe, confident, protected, challenged, nurtured i could go on and on. but most importantly you grew flowers in the darkest parts of me (said perfectly by the one and only Zach Bryan) i didn’t think it was possible to find someone who could stand beside me, and give me every ounce of encouragement and love as i put back together the most broken parts of myself. i finally feel whole.”

Joy also thanked Viall “for being the man you are,” and added, “i can’t wait to marry you!!!!”

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