FROM the Bee Gees to The Kinks to The Everly Brothers to Oasis, siblings and family members in creative partnerships have long been a feature of the rock and pop world, and often with explosive results.

They're still the exception rather than the rule, however. But in the genre of folk, roots and country music – the stuff which makes the annual Celtic Connections festival tick – it sometimes feels like the other way round. Here is a world in which music is often performed at grassroots level un-amplified and in intimate surroundings such as family get-togethers, and where the music itself comes from ready-made songbooks which encourage participation across the ages. It's no surprise, then, that those families which come together over music in the home often end up on the road together as well.

It's dangerous to over-romanticise the role of folk music as a sort of domestic glue, but nobody can fail to discern a certain clannishness in its practitioners or ignore the way the familiar names seem to crop up again and again, year after year.

To mark the fact, the 2016 Celtic Connections festival features a strand called Family Ties. As well as emphasising and celebrating the blood bonds between musicians, it nods to the looser links between the festival's wider family of players and even to connections between cities, notably Glasgow and Marseille (twinned a decade ago next year), as well as Edinburgh and Dunedin, on New Zealand's south island.

Of course no Celtic Connections festival would be complete without a member of the Waterson-Carthy dynasty present, and British folk music's first family is represented in next month's festival by Martin Carthy and daughter Eliza. Likewise Brian and Eithne Vallely, founders of the Armagh Pipers Club, celebrate its 50th anniversary with a concert featuring traditional Irish groups Lunasa and Buille, the two bands formed by their three sons, Cillian, Niall and Caoimhin.

But grabbing the familial limelight this year are two acts featuring sisters who owe their musical careers to the nurturing environment surrounding them as they were growing up. They are Rachel and Becky Unthank, from the north-east of England, and Martha Wainwright and her half-sister Lucy Wainwright Roche, from Montreal and New York respectively.

It's almost a cliché, but the Unthank sisters were raised in a domestic environment in which everyone sang and played, and where even the children were expected to do a turn. Their father was a member of Northumbrian folk group The Keelers and as young girls Rachel and Becky also took part in clog dancing competitions. In 2010 they even presented a BBC Four documentary on the subject.

The way elder sister Rachel tells it, their music-making is an integral part of the emotional ties binding the pair.

“When Becky was really young, she would only sing if I sang with her,” she has said. “So it sort of grew from there. It has always been a part of our relationship. When I left home and went to university, we would sing together on the phone. It is a good way to explore your relationship. We find the harmonies really comfortable. It's just, 'You try that bit, and I'll do this bit'.”

Martha Wainwright and Lucy Wainwright Roche have the same father – Loudon Wainwright III, father also of Martha's brother Rufus Wainwright – but different mothers. Martha's is late Canadian folk great Kate McGarrigle, who performed with her own sister, Anna. Lucy's is Irish-American singer Suzzy Roche, who performed with her sisters Maggie and Terre as The Roches in 1970s New York.

Continuing that strong distaff tradition, Martha and Lucy now perform as The Wainwright Sisters, a collaboration born in part when Martha recorded a CD for Lucy's children comprising lullabies she had learned from her own mother. Some of those songs, as well as compositions by Suzzy Roche, Loudon Wainwright III and Kate McGarrigle herself, feature on the Sisters' debut album Songs In The Dark, released last month and drenched in themes of family and childhood. Making it truly a family affair, Anna McGarrigle also performs on the record.

Turning to the men, another folk dynasty scion performing at Celtic Connections is Teddy Thompson. As with the Wainwright family, whose various members have a long habit of airing domestic grievances in public through their barbed songs, his most recent album, Family, speaks as much of familial discord as it does familial harmony: Thompson is the son of Fairport Convention founder Richard Thompson and his estranged ex-wife, folk singer Linda Thompson, and Family was his attempt to bring them together on record again. Also invited were Thompson's sisters, Kami and Muna, his nephew Zak and his half-brother, Jack. In fact every note on Family is played by a member of the extended Thompson clan.

“I came up with this project to get everyone back together,” Thompson told music magazine Uncut when the album was released last year. “I was really trying to heal some wounds for myself, but I dragged everyone along with me.”

As for the cities, well it's a question of close twins and distant cousins. On January 27, Sister Cities features a coming together of musicians from Edinburgh and Dunedin, the New Zealand city founded by Scots and famous for having streets and suburbs whose names echo those in the capital. Showcase Scotland, meanwhile, welcomes a roster of French talent to Glasgow to celebrate connections between Scotland and France and in particular the 10th anniversary of Glasgow's twinning with Marseille.

Celtic Connections has always been a family affair: this year, though, it celebrates the fact.

The Music And The Land featuring Freeland Barbour, Martin Carthy and others is on January 19 (Old Fruitmarket); Armagh Pipers Night featuring Lunasa, Buille and Flook is on January 20 (Old Fruitmarket); Songs Of Separation featuring Eliza Carthy and others is on January 24 (Mitchell Theatre); The Wainwright Sisters perform on January 25 (City Halls, Grand Hall); Teddy Thompson performs on January 27 (Glasgow Royal Concert Hall, Main Auditorium); Sister Cities is on January 27 (The National Piping Centre); Showcase Scotland runs from January 27-31 (various venues); The Unthanks perform with Lau on January 28 (Glasgow Royal Concert Hall, Main Auditorium)

The Sunday Herald is media partner of Celtic Connections. For full programme details and tickets visit www.celticconnections.com