The 73-year-old actor will officiate at the ceremony between his friend and 'X-Men' costar and Ozell, when they tie the knot in Masachusetts, reported USA Today.
"I'm going to marry Patrick Stewart. I am going to officiate at his wedding. In Massachusetts, in the middle of America somewhere, you get a friend along, and I read out the words, and Sunny and Patrick will then be married," McKellen said.
The British actor revealed it won't be the first time he has officiated at such a service.
Massachusetts' Secretary of Commonwealth offers a service that allows a family friend or relative to perform a couple's wedding ceremony for a fee of USD 25.
Patrick, 72, and Sunny, 35, have been dating since 2009.