Loved ones who have been in regular contact; loved ones who see each other only rarely; loved ones who have been apart for years - across the world they are being reunited in their differing circumstances this week.

But rare even at this time of year is the reuniting of family members who had never known of the other's existence.

Rodney Bickerstaffe, leader of Britain's biggest union, Unison, has spent almost half a century knowing neither where he came from nor what a place in Dublin held for him. The place - Cabra - he has just discovered holds three Irish brothers.

Tommy, Peter and Liam, though younger than and, until now, unknown to Rodney, share with him a resemblance of sorts to their father, Tommy Simpson.

As a carpenter in London in 1944, Tommy went into casualty with stomach pains. Elizabeth Bickerstaffe was the nurse on duty and a four-month romance ensued; a pregnancy followed, and though Elizabeth wrote to Tommy's teenage sister Maureen to tell her of the birth of Rodney Kevan Bickerstaffe on April 6th, 1945, Tommy had returned to Dublin and never got in touch again.

"The truth is," says a throatily Yorkshire-accented Bickerstaffe today, "I was six when I started school, when it hit me that I was different. Beyond that it was only now and again that I wondered why I didn't have a father."

His mother had brought up the young Rodney in a single mothers' home before moving back to Doncaster to live with her parents.

"I knew my dad's name," says Rodney, "and I had a small passport-size photo of him, but beyond that I was not driven to know much more about him. When my mother married my step-dad was so good to me I assumed it would be destabilising to the family set-up to look for another father."

Having won a scholarship to Doncaster Grammar School, he rose through the public employees' union NUPE and was behind the merging of three unions into Unison. He is now to the fore in establishing a statutory minimum wage in Britain.

It was not until the death of his step-father in 1990 that thoughts turned again to the possibility of an extended family, though it wasn't until this year that he asked his mother if she would mind if he tried to look up his past.

"She had this address in Cabra. When I was over in Dublin at the end of September at the Public Service International Conference, I was chairing a meeting on Sunday 20th which finished earlier than expected.

"So I asked one of the IMPACT members if they knew where this Cabra was and he said it was about 10 minutes away." In a taxi on the way to the airport he decided he would visit the address in Cabra, which he says he fully expected would have long forgotten any mention of the Simpson family.

"In a way, I suppose, I just wanted to see the house and close the story."

The house - as it turned out Tommy Simpson's father's house - was still in the family. Tommy's youngest sister, Aileen, has retired and still lives there with her husband. The couple however were on holiday in Portugal.

Fortunately a neighbour, working in his garden that Sunday afternoon in September, recalled Aileen's maiden name was Simpson. He sent Rodney to another house, the home of another aunt.

After toing and froing between aunts and cousins, word reached Rodney's half-brothers, Tommy, Liam and Peter, through their now elderly aunt Maureen, of their half-brother. Tommy, their father, had died in 1991.

Rodney spoke to his brother Tommy Simpson for the first time, by telephone, at 11 p.m. on Monday, September 28th.

"It was very emotional," says Tommy. "He called me and said something like `Howya matey?' We were both nearly in tears.

"Our interests are uncannily similar. I'm on the SIPTU branch committee for FAS and also involved in the Green Party, and I was going to be going over to London in November. So I said I would meet him then. And he said `Oh no, I'd love to hop on a plane this week.' "

The following weekend Rodney travelled to Dublin with his wife, his son and half-brother, where the middle-aged brothers encountered their middle-aged half brother for the first time.

The happy episode has led to a jibe or two from such luminaries as the British Prime Minister, Mr Tony Blair, who commented: "Fancy waking up in the morning and finding that you've got Rodney for a brother."

Tommy Simpson the younger says of the reunion that he and his brothers never had any doubts that they wanted to meet Rodney. Tommy the elder had never mentioned Elizabeth and it is probable he never knew of Rodney. But Tommy today says he sees the unexpected family addition as "a very positive thing. It adds to the relationships you've already got more than threatening them, and Rodney is such a warm and kind person."

Of the Simpsons, Rodney says he has been touched by their hospitality and willingness to reach out. "When I went to that house in Cabra I thought it would be the end of a story, and it has turned out such a wonderful bonus."