Country music fans are still in shock over Blake Shelton and Miranda Lambert's Monday announcement that they are divorcing.

The celebrity couple seemed very much in love. What happened?

TMZ reports Shelton filed for divorce because he believed Lambert was unfaithful, not once but twice.

Multiple sources close to the couple said Shelton suspected his wife of cheating for months. He reportedly heard rumors she had an affair with country singer Chris Young.

Young opened for one of Lambert's concerts a few years ago. The two were seen together publicly, but there never was an indication of anything between them other than friendship.

Sources also said Young was not the reason for Shelton filing for divorce; Lambert was allegedly seeing another man, who is not a country singer.

Shelton filed for divorce two weeks ago because he reportedly received undisclosed information about his wife and the other man that established the rumor as fact.

The couple released a statement saying the divorce is amicable, but TMZ was told Shelton has been very upset and told Lambert that she needs to remove her animals from his Oklahoma ranch by Monday.

People magazine reports, since their marriage in May 2011, there have been persistent rumors of infidelity on both sides and marital trouble.

The tabloids frequently reported on Shelton's wandering eye, but the country star told People in 2013 he gave his wife access to all of his electronics in case she needed reassurance.

"[I tell Miranda], 'I have nothing to hide from you,'" Shelton said.

"That's always been our policy: 'Here's my phone. Go through it.' That's really the kind of trust we have. There are no secrets. [I'll say], 'Go dig through my drawers or my computer if you feel like you need to.' And that's been a really good thing, because I don't want her to ever have any doubts."

When rumors in March 2013 suggested Shelton had hooked up with another singer, the couple used social media to defend their marriage.

The "Lonely Tonight" singer told People in late 2012 that his wife was the one who made sure they maintained a healthy marriage and saw each other despite hectic work schedules.

"She literally has flown across the country to be with me for one night and will get up and go home the next morning ... where I just won't do it and say, 'Oh, I'll see you next week!'" Shelton said. "I'm just a guy about it, I guess. She's always been the one to go through hell to make sure we spend time together."

Shelton and Lambert first met in 2005 when they collaborated on a Country Music Television show while "The Voice" coach was still married to his first wife, Kaynette Williams, who he divorced a year later.

Shelton and Lambert dated for six years before marrying in her native Texas four years ago.