Pregnant Joanna Gaines shared black and white portrait of the couple on their wedding day

The 40-year-old reality TV star and mother-of-four, Joanna Gaines, is expecting her fifth child. The couple celebrated their wedding anniversary on Thursday.

Joanna took to Instagram and congratulated Chip on reaching the 15-year mark in their marriage. She shared their wedding photo with her 7.5 million followers.

She wrote in the caption: 'It's been a good fifteen years, [Chip Gaines, heart emoji] Here's to fifty more.' It was a firm-favorite with her followers, accumulating more than 1.4 million likes in less than a day.

Chip wrote a poem for their anniversary and shared it on Twitter: '15 years, where'd they go, 15 years, I'd like to know, 15 more, to God I pray, 15 more just to make her day.'

As reported by People, the couple met in 2001 while Joanna was still working for her father. The pair exchanged vows two years later, and their first child was born in 2005.

They also share 11-year-old Ella, 9-year-old Duke, and 8-year-old Emmie Kay. The children cannot wait to meet their brother, expected to arrive sometime in June or July 2018.

The reality TV stars announced the pregnancy in back in January when they uploaded an adorable photo to Instagram which shows Chip with a baby bump.

Many fans are sad that the couple's reality show came to an end, but they haven't seen the last of the Gaines Familly just yet. The couple has a collection of home decor items available at Target.

They also opened a new restaurant called Magnolia Table, and Joanna's new cookbook of the same name was released last month.

The Gaines' might not have Fixer Upper series anymore, but their company Magnolia Design and Construction will continue to restore and renovate homes.

Fans can look forward to Magnolia Kids as well. The store will launch in the upcoming months, and branded apparel, baby clothes, and kids' decor items will be sold in the online store.