Working side by side in their new sunlit prem in Oakland, California, making custom-made books in leather and cloth, everything seemed to be coming together for husband-and-wife team Ivar Diehl and Danya Winterman, co-founders of The Key Printing and Binding. But their marriage was in difficulties and last year they separated. But first they made a vow: “We promised that if we split up we would try to keep our business partnership going. It would have been too great a shame to destroy something we had built together,” says Mr Diehl.

Co-founder couples who remain wedded to their business after ending their marriage may not be common but they are becoming less rare. Abba, the double-couple band that became double-divorced, continued to record hits after Agnethaand Ulvaeus split, although the next divorce brought the curtain down. Eighteen years after separating from the hairdresser Nicky Clarke, Lesley Clarke still directs the business side of the eponymous salon and haircare brand. The restaurateur Rick Stein and his former wife Jill divorced eight years ago but continue to open new ventures together, with Ms Stein designing the interiors.

And in start-up land, couples who go into business together and fall out of love are a recognised phenomenon. “It’s an archetype we see more and more because succeeding at marriage is hard enough without the added stress of running a business together,” says Mich Crosby, co-founder of Wevorce, a San Francisco-based business that helps couples in business divorce amicably.

Some estranged couples cannot to buy each other out and soldier on as business partners out of necessity. Ambition, loyalty to staff and respect for each other’s talents can all be influential too — the flamboyant Mr Clarke, for example, has said that without the guiding acumen of Ms Clarke he would not have had a brand. But when couples can no longer live together, what hope is there that they will see eye to eye as business partners?

Before addressing the commercial of a break-up, Ms Crosby, who is divorced, advises couples to tackle the pain — especially if one side has been unfaithful — in order to the emotional needs from the legal and financial resolutions that must be reached. Otherwise the likelihood is that resentment will fester and make working together impossible. “What we often see is ‘the betrayer’ throwing in a lot of money in an attempt to fix things, and in six months the settlement comes unstuck because the betrayer no longer feels guilty and the other party is still angry,” Ms Crosby says.

Sometimes estranged couples are doing fine professionally; then a wound reopens, emotions resurface and the whole thing starts to unravel. One co-founder, who asked not to be named,how office relations soured when she began dating again. “[My ex] began behaving as if he could no longer trust me [with the even though our break-up was amicable.”

Perpetual fireworks are probably a sign that the estranged couple are no more compatible as business partners than as spouses, but occasional upsets are generally survivable so long as both sides share a goal and are willing to be generous, say those with personal experience. Ms Winterman and Mr Diehl agreed for the sake of their baby daughter and their business to treat each other with the consideration due to old friends, taking breaks to cool off when the stress of meeting production deadlines and dissolving their marriage at the same time became too much.

“When you know someone so well, a tone of voice that’s a little off can be a really emotional thing,” says Ms Winterman. The levelheadedness of a third co-founder who is a trusted friend has them navigate “some of the weirdness”, of the situation and “kept us slightly better behaved than we might otherwise be”, she adds.

Strategies that conventional business partners employ to avert gridlock — from consulting a neutral party to flipping a coin can also help exes resolve workplace disagreements peaceably. Ms Crosby, who once hired her ex-husband as her operations head, warns that when former spouses argue, old patterns of confrontation resurface.

To avoid being sucked into fights, she advises couples to heed normal office etiquette in their dealings with each other. Recalling a pricing disagreement with her ex that turned personal in public, she reflects that “an ex knows what buttons to push [to rile you].”

Keeping rumour-mongers at bay is often a concern when co-founder couples split, as suppliers may fret that the business will fold and employees fear for their jobs. British couple Louisa Scott and Jez John over what to tell staff at their jointly owned businesses Webstars, a digital agency, and Make My Day, a music business, when they separated in 2006.

Eventually, Mr John broke the news matter-of-factly during an office briefing devoted mainly to plans for expansion. In the following months, the couple spoke often — and even joked in public — about their separation, emphasising that nothing other than their domestic arrangements were about to change. “I think initially the staff worried that the family feel in the office would change. But the fact that we were very open, coupled with Jez’s bad jokes, helped to take away the awkwardness of the situation,” says Ms Scott.

A domestic break-up will oblige co-owners to rethink how they make decisions and share information. Divorcees Rick Rivera and Lisa Layton, co-owners of American Car Craft, an auto accessories business, say they work better as business partners than they ever did as a couple. But they miss the nonstop talk that spilled over from the office into domestic life. “We discussed business all the time, even in bed,” says Ms Layton. “I feel it takes us longer to make things happenwe had regular meetings the business would grow faster.”

For some couples a break-up highlights a need to adapt as the business matures. Mr John and Ms Scott say they now run decisions past each other rather than assume that they know the other’s opinion.

Having to pay the bills for two households while carving out a business niche has prompted Mr Diehl and Ms Winterman to diversify from purely bespoke work into making notebooks and journals decorated with graffiti art for galleries and writers’ stores.

Working in the sight line of an ex is nevertheless awkward, Ms Winterman reflects. “In the past, Ivar would often show up for me an hour late. Now he runs out of the office to meet his girlfriend at the exact right moment. That’s really annoying to watch.”