'RHOBH's' Yolanda & David Foster Divorcing: Co-Star Kyle Richards Reacts [VIDEO]

Yolanda Foster and David Foster are getting divorced after only four years of marriage, making the announcement in a joint statement. Foster's RHOBH co-star Kyle Richards reacts to the divorce on Watch What Happens Live.

Yolanda, 51, and David, 66, issued a statement to People, saying, "Sadly we have decided to go our separate ways. We've shared nine beautiful and joyous years together. During that time we experienced love, friendship and the inevitable challenges that come with managing a marriage, careers, blended families and health issues."

RHOBH fans have watched the 51-year-old former Dutch model struggle with health issues the past few years. She was diagnosed with Lyme Disease in 2012.

Foster admitted in the past that he failed to support his wife at times with her health struggles.

He previously revealed, "I fail some days. You know, I get cranky and then I realize that she’s got it 100 times worse than me. But I just do my best."

Foster has a busy schedule and can't always be by his ailing wife's side. He writes her love letters to show his support.

The reality star has three children from her first marriage to Mohamed Hadid – Gigi 20, Bella, 19, and Anwar, 16.

Grammy award-winning Foster has been married four times previously and has five daughters.

Yolanda's RHOBH co-star, Kyle Richards, appeared on Bravo's Watch What Happens Live and discussed the divorce announcement.

Richards reacted to the news, saying, "Very sad. In some ways, yes [it was a surprise]. I mean, we didn't know. But I think that they've been struggling, and Yolanda's been so sick – I don't know if that has anything to do with it, I have no idea, but it was just really sad."

The 46-year-old reality star adds that she reached out to Foster after hearing of the divorce.

Richards worries about her co-star dealing with Lyme Disease and a divorce at the same time.