Labour leader Ed Miliband has announced he is getting married in May - but elder brother David will not be best man.
Mr Miliband, 41, is to tie the knot with long-term partner Justine Thornton at a hotel ceremony near Nottingham attended only by family and "very close" friends.
The small-scale wedding will not include a best man, avoiding the thorny issue of whether Mr Miliband would ask David - whom he beat to the Labour leadership last year - to fill the role.
As the first leader of a major political party to live with his family out of wedlock, Mr Miliband has faced criticism about his unmarried status.
A beaming Mr Miliband said he had proposed on Primrose Hill, commanding panoramic views of the capital, near their north London home.
Standing with Ms Thornton, a lawyer, he said the May 27 wedding would involve only "family and very close family friends".
"We will do it in our own way. We have done everything in our own way," he told BBC News.
His brother David, who had Ed as his best man, had been the second person to whom he broke the news after their mother, Mr Miliband said.
"He is delighted for me and he will obviously be there."
The ceremony will be at Langar Hall hotel, not far from where Ms Thornton grew up, followed by a honeymoon in an undisclosed location.
Mr Miliband and his bride-to-be have been together for several years and have two sons, but the Labour leader previously said he had been "too busy" to get married.
The couple announced the date in an interview with the Doncaster Free Press, the local newspaper in Mr Miliband's Doncaster North constituency.
He told the newspaper it was "the right time" for the couple to tie the knot and that they had decided they would get married about a year ago.
"This is going to be a fantastic day for us both and I feel incredibly privileged to be marrying someone so beautiful and who is such a special person," he told the newspaper.
He added: "At the end of the day we're in our 40s and we've got two kids - so it wasn't a case of me suddenly popping the question. This is just something we think is right for us."
There might be a "low key" stag night though, he disclosed.
Ms Thornton said: "Ed wasn't even an MP when I met him and at the end of the day I am marrying him because of who he is and not because of what he's doing now.
"We're planning on a small ceremony, all at the hotel with everything at the same place and we're looking forward to it very much."
In the Commons this afternoon, Prime Minister David Cameron offered his congratulations when he faced the Labour leader at question time.
"On behalf of everyone in the House I can congratulate you and Justine on the happy news of your forthcoming wedding and, I am sure with everyone, to wish you a long and happy life together," he said.
Unable to resist a dig at his adversary, he added: "When I was Leader of the Opposition I would have done anything to have a honeymoon. He probably feels the same way."
Mr Miliband joked that he might ask Mr Cameron for advice about his stag night - a reference to the Prime Minister attending his future brother-in-law's just days before hitting the campaign trail ahead of the election last year.
Mr Miliband has been frequently questioned about his marital status since becoming Labour leader last September.
He has insisted in the past that voters are "pretty relaxed" over whether or not politicians were married.
He also faced embarrassment after it emerged he was not listed as the father on first son Daniel's birth certificate.
Because they were unmarried, Ms Thornton was unable to add both parents' names when she registered the birth and Mr Miliband did not get around to going in person.
The couple's younger child Samuel was born in November last year.
In an interview with Piers Morgan for GQ magazine last year, Mr Miliband insisted he would not be pushed into marriage for political reasons
"The more people who challenge me on it from a political standpoint, the more resistant I will become," he said.
"We'll get married because we want to get married and love each other very much, no other reason."
After a constant ribbing about his marital status, he joked at one point in the interview: "She's not my wife. Thank God for that, probably."
The Labour leader met Cambridge-educated environmental barrister Ms Thornton, who is a year younger than him, in 2005.
She works as a barrister for the 39 Essex Street Chambers in London and has earned plaudits for her work, described by Chambers and Partners in their 2010 directory of the legal profession as "intelligent, thorough, enthusiastic and pleasant".
She has worked for high-profile clients, including a period spent acting as an advocate for the Welsh Assembly Government and also worked as a government adviser on the environment and biotechnology.