Frank spokesman Harry Gural said the liberal Massachusetts Democrat's wedding will be in his home state, but that no date had been set.
Ready, 42, lives in Ogunquit, Maine. He has a small business doing custom awnings, carpentry, painting, welding and other general handyman services, Gural said. Ready is also a photographer. The two men have been together since spring 2007.
Frank was attending a retreat Thursday with other House Democrats on Maryland's Eastern Shore.
During an appearance on PBS' "The Charlie Rose Show" earlier this month, Frank said he was looking forward to leaving Congress and spending time with Ready.
"Look, I have a partner now, Jim Ready; I have an emotional attachment. I'm in love for the first time in my life," Frank said on the show.
Gay rights supporters saluted Frank's engagement but noted that because of the federal Defense of Marriage Act, known as DOMA, Ready would not enjoy the same rights as other spouses.
DOMA blocks the federal government from recognizing same-sex unions and says states that don't have such marriages don't have to recognize marriages performed in states that do.
"It is, of course, somewhat ironic that because of DOMA and because Barney is a federal employee, Jim won't be eligible for any of the benefits that any other spouse would be able to get," said Lee Swislow, executive director of Gay & Lesbian Advocates & Defenders, the Boston legal rights organization that brought the case that led to Massachusetts becoming the first state in the country to legalize gay marriage.
"I think it's always positive when public figures are role models in these critical societal institutions," Swislow added.
Frank, 71, won his House seat in 1980 and was one of the first lawmakers to come out of the closet.
Ready has made some headlines in recent years with Frank.
He was charged in August 2007 with marijuana cultivation for allegedly growing more than five marijuana plants on his property, records from the York County, Maine, district attorney's office show. That charge was dismissed after Ready complied with a deferred disposition agreement and admitted to a charge of civil possession of marijuana.
Frank later told the Boston Globe that he was at Ready's house when Ready was arrested, but that he never saw the marijuana and has never smoked any. Frank has also said Ready has promised him never to repeat his mistake.
During Frank's 2010 re-election bid, Ready had a brisk exchange of words with Frank's Republican challenger Sean Bielat after the candidates debated. Ready was taking photos of Bielat.
A Boston Herald video showed Ready saying, "You better get used to it, dude," after Bielat asked him about the photos.
Ready then said, "It's a free country, isn't it?" and a chuckling Bielat replied, "It sure is, at least if we can get the Congress back."
Frank's campaign at the time said that Ready was an amateur photographer who took pictures at many campaign events and that no harm was intended.
Last November, Frank announced that he was retiring at the end of his current term, his 16th in Congress.
He said he was retiring because his Massachusetts district has changed so much he would have to spend too much time campaigning for re-election.
Frank has been in the House since 1981 and represents the state's 4th District, which stretches from the upscale Boston suburbs of Newton and Brookline to the working-class cities of New Bedford and Taunton in southeastern Massachusetts.
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