I may not be getting this entirely correct – it was a long time ago – but I am fairly sure that the only time I saw the band Family live, at Glasgow Apollo on their valedictory tour, Scotland were playing Czechoslovakia in a crucial World Cup qualifier the same night.

At 15 I had nailed my colours firmly to the music mast, but front man Roger Chapman kept us informed of the progress of the game anyway, disappearing into the wings to ask a roadie with a radio the score.

I only just caught the band during their performing existence, but I had their most recent albums then and when my 18th birthday yielded a sheaf of record tokens, I filled in the gaps in my collection. What I Iiked most about Family, I think, was that they never made the same album twice. All eight of them are good, but very different, and only Chappo's distinctive powerful bluesy vibrato voice really marks them out as being the work of the same group.

Anyway (the title of album four, curiously), you needn't take my word for it, because reissue specialists Snapper Music are about to unleash a lavish boxed set of the band's entire recorded works, complete with a lost live album, rarities and out-takes, and a 72-page book. And the band, or at least as comprehensive a version of it as is feasible, are committed to playing two dates at Shepherd's Bush Empire at the start of February. This incarnation will include founder members Chapman and drummer Rob Townsend alongside long-servers Poli Palmer and Jim Cregan. It will be 40 years since the group last played.

"The impetus for the re-issue came from the record company," says Chapman, "and they've done a splendid job. There's lots of stuff that's never been collected before, and the book is a good read and accurate, I think. I've found out more about myself than I knew 40 years ago."

It is not true, however, that Family "never had a book written about them," as Chapman originally suggests. They were, it was well known, the chief subject of Jenny Fabian's controversial 1969 novel, Groupie, thinly disguised as "Relation". The book explicitly lifted the lid on the activities of girls who follow bands around, some time before Pamela des Barres's notorious I'm With The Band.

"Jenny was a really good friend," Chapman remembers with a throaty chuckle. "We all lived in the same house in Chelsea with our manager. There were seven rooms for the crew, the band and Jenny. And when we came back from America some of us, including Jenny, took an apartment in Exhibition Road in Kensington."

In fact Chapman's memory of his entire career is pretty good, considering. He passed his 70th birthday last year and still performs in the company of his own band The Shortlist – which has also included some of the same faces for decades – including an annual date in his native Leicester.

"Of course we didn't start as Family, we started as The Farinas, playing R&B, blues and soul. Then Charlie and I started to write. We had songs of our own that we had to arrange ourselves, and they became very off-the-wall arrangements. The band never had more than five members and it was good for as long we were all keen to make good music at the same time."

Family were playing at the same time as Cream and Jimi Hendrix at places like the UFO in Camden and the Isle of Wight Festival. Those were heady days. "The drugs and alcohol came from different sources. Some were druggies and some were drunks. For me the drinking came later, I always had a little pocket with various substances to take you up, down or sideways."

"Charlie" is Charlie Whitney, guitarist and Chapman's songwriting partner in Family and their following group, Streetwalkers. He is the notable absentee from the reunion.

"I don't see Charlie – he lives on a Greek island with his partner – but we are in touch two or three times a year by email. He didn't feel he could do it, so good luck to him – and have a good time."

Chapman says it has been a real "memory jag" going back over the old material, very little of which he has sung since. The hit single from 1972's Bandstand album, Burlesque, gets an annual outing in Leicester and he occasionally responds to requests for Weaver's Answer or encores with an a cappella My Friend the Sun, but that has been all. After Streetwalkers, Roger Chapman and the Shortlist did most of their touring, and recording, in Europe – and especially Germany, where no-one ever asked for Family's music.

This time out, Chapman is not even promising that the band's best known songs will get an airing. "We'll cover the gamut of the catalogue, but not what the audience will expect. We never did follow the audience route, so why should we start now?"

When he says of the London gigs that they are not a question of the money, it is believable that Chapman is quite sincere. His solo operation would be a lot less hassle for that.

"I am still healthy and so is Rob and we are both still musically involved. I've always been a writer, but on the financial side of the business you make money touring. Now I sit back a little, but you have to keep moving, like a shark. You can't stop because then you are dead.

"But this is the biggest project. The music is so diverse and we have done no gigs since the farewell tour in '73, and never looked likely to. It's like putting on a West End musical for two days and I am a bit nervous of it. There's a pride in the event – you don't want to let the people down"

Of course there is always the possibility that Family: Once Upon A Time may not be quite the end of the story.

"We are getting offers to continue," Chapman concedes, non-commitedly, "and now the Streetwalkers back catalogue is being looked at. . ."

Family: Once Upon A Time is released on February 4 and can be pre-ordered at www.familyonceuponatime.com. Family play O2 Shepherd's Bush Empire on February 1 and 2.