In Relatively, a new podcast about sibling relationships, the television presenter and historian Dan Snow contemplates his behaviour towards his younger sister, the documentary film-maker Rebecca Snow, when they were children. “The greatest regret in my life is how horrible I was to my little sister,” he says.

He recalls trying to drop a pair of scissors on her when she was a baby, which he calls “a proper homicide attempt”. After that, he restricted his methods to psychological torture­ — “I thought that by reducing her self-esteem, maybe that would help build up mine. To this day, I find it extraordinary [that] I did that.”

The podcast is presented and produced by Catherine Carr, who made one of my favourite BBC radio series of recent years, Where Are You Going?, in which she asked the same question of travellers across the world, prompting fascinating responses that revealed much about how we live, work and find escape.

Relatively is predicated on a similarly simple concept, in this case a single relationship as a gateway to a person’s life and character. Sibling relationships are often the most long-lasting relationships we will have. They can be messy and laden with baggage, but they can also thrive on shared experiences and understanding, and can evolve from rough-and-tumble silliness to solid friendship.

The series­ — which has also featured the Labour MP Jess Phillips and her brother Luke, and the actor Johnny Flynn and his sister Lillie — is also a neat twist on the ubiquitous celebrity interview podcast, not least because it brings much-needed focus and depth to the conversation. Amid the larkiness and nostalgia, there are moments of great seriousness and poignance.

The Snow siblings, who were born 18 months apart, reveal a changing relationship during which, in their late teens, they became close, began socialising together and even dated one another’s friends. Now they live on different continents but talk frequently and take pride in one another’s successes.

Most interesting are their differing takes on their early relationship and the subjective nature of memory. While Dan continues to agonise over the pain he inflicted on his sister, she bears her own scars, though these have less to do with being bullied by Dan than how she treated their youngest sister, whom she teased mercilessly. “So I’m responsible for a multigenerational trauma,” says Dan. “Exactly,” Rebecca agrees.

Sibling Revelry, hosted by the actor Kate Hudson alongside her brother Oliver, is another podcast that attempts to unpick this knotty relationship — with dubious results. Inevitably, the pair bring an impressive roll-call of guests, among them Zooey Deschanel and her sister Emily; the brothers Matthew and Rooster McConaughey; Dakota and Elle Fanning and the Haim sisters.

The snag here is that the Hudson siblings are terrible interviewers who talk about themselves, talk over each other and everyone else, and generally treat the exercise like a chummy catch-up session. Fun for them, no doubt, but tedious for everyone else.