The 23-year-old British folk singer, who introduced the 50-year-old former "Friends" star and the 38-year-old Snow Patrol rocker to each other, is said to be one of ushers at the couple's wedding, which is rumored to be held in Ireland later this year.
Ed Sheeran To Be The Best Man At Courteney Cox And Johnny McDaid's Irish Wedding?
"Johnny's other best pal, singer Foy Vance, is also an usher," added the tipster. "It's between him and Ed for best man -- they'll probably share it."
After the wedding in Ireland, it is expected that the couple will hold a follow-on bash in California, according to MTV UK.
The "Lego House" hitmaker confirmed he had played matchmaker to Cox and McDaid late last year, and admitted that he was thrilled to see them happy together.
"I go out a lot - to meet people, hang out and bring my friends to house parties. This was one of those nights, and I brought Johnny along with me and introduced them," he previously said in an interview, according to Belfast Telegraph. "At the end of the night I went home, and he didn't. That was it."
Cox's upcoming wedding to McDaid is going to be her second trip down the aisle. She was previously married to actor David Arquette from 1999 to 2013, but she is said to be happier ever since meeting the musician.
''She has never been happier," added The Sun's source. "And even though it's her second marriage, she would like people important to her to be there.'"
Cox and McDaid announced their engagement via Twitter on June 26.
"I'm engaged to him," Cox wrote on the microblogging site, along with a beach selfie of her with the 37-year-old Irish rocker. McDaid also took to his Twitter account to share the good news, writing, "I'm engaged to her."