Hollywood loves power couples. Over the years, we've seen movies about married lawyers (Adam's Rib), married scientists (Outbreak), and married professional killers (Mr. & Mrs. Smith). But I can't think of any movies about married entrepreneurs. That's a missed opportunity, because the potential for both drama and comedy is legion.

In real life, entrepreneurs do end up together, for a variety of reasons. Some meet after they've already started their companies--at trade shows or chamber of commerce events or CEO networking groups. Others agree to take turns starting businesses after they marry, the way some spouses take turns attending graduate school. Occasionally, a nonentrepreneur marries an entrepreneur and then wants to try what his spouse is doing, because, man, that looks like fun. But however they get there, two spouses running two companies doubles the chaos. Or more than doubles it: The absence of one adult able to maintain a semblance of normalcy introduces a multiplier effect.

The chief sources of stress are (of course) money and time. Entrepreneurship requires households to put up cash before they start earning it. It's an investment that works best--sometimes only--if one family member shores up the dam with a regular paycheck and health benefits. The schedules of conventionally employed spouses are usually more predictable than those of entrepreneurs, which is critical when there are children in the mix. Employed spouses also get paid vacations. That means one adult is not working a full-court press 52 weeks a year, so a little pressure is being released somewhere.

When one spouse owns a company, that business competes with the family for resources. When both spouses own companies, his business may compete with her business, and both businesses compete with the family. If both spouses' companies go through difficult stretches at the same time, they are like twins in the womb: One may be fed at the expense of the other. With win-win not an option, the couple must negotiate who loses more. Which spouse will skip a paycheck? Which will dip into savings? Who will have to lay off an employee?

Because most marriages are founded on an ideal of parity, spouses may be tempted to share the sacrifice, as they vowed to share pretty much everything in that innocent moment standing before the altar. Or the entrepreneur who is in less dire straits may want to help her flailing spouse, even if she can't really afford to do so. But the mathematics of family survival don't work that way.

So, for practical reasons, many two-entrepreneur families choose which company to favor based on the relative contribution of each to the family's income. That's the understanding in the Flynn household. Lisa Flynn is founder of ChildLight Yoga and Yoga 4 Classrooms, New Hampshire-based companies that teach yoga and mindfulness to children. Her husband, John Flynn, runs Great Works Properties, a property and golf-course management company. John's business brings in most of the cash, so "if push came to shove," said Lisa, "his business would take precedence. But that's tough for me to admit out loud."

The problem with such arrangements is they tend to perpetuate inequities. How likely is it that two businesses, even with comparable ambitions and resources, will progress along exactly the same trajectories? If a couple's two companies have lopsided revenue, that can force uncomfortable--and sometimes premature--discussions about their respective viability. Such discussions get ugly when one spouse calls into question the other's seriousness, even if it's only in comparison to his own. The leap from "which company is healthier" to "which company is worthier" is both dangerous and easy to make. Suddenly, it's my growth company versus your lifestyle company. Or worse, my business versus your hobby.

The same calculus comes into play with schedules. It's easier to decide which spouse forgoes a sales trip or works the weekend when there is a primary family business and a secondary family business. But when spouses don't agree which is which, bad feelings are inevitable. If there are kids, then the prospect of running two start-ups while raising a family becomes like riding a unicycle on a high wire while juggling lit torches. I know people do it. But if I had to watch them, I'd keep my hands over my eyes and peek through my fingers.

Some dual-company couples don't compete for resources--they just compete. Lisa Landry owns the New Hampshire-based marketing firm Savvy Workshop. Her husband, Joe Landry, is founder of Build Savvy, a construction firm. "At the end of the day, we have to show each other our numbers," said Lisa. "Sometimes, when Joe's business is doing great and mine isn't, I get jealous. I even try to beat him at Monopoly."

Or the entrepreneur whose company is doing better is tempted to offer advice to his struggling spouse. Such counsel may be appreciated or insufferable, depending on the spirit in which it is given. Mason Arnold is founder of Greenling, an organic-food delivery service based in Austin. His wife, Mylie Arnold, owns a large dance studio. Mason described how the couple de-fanged the tension that arose when they gave each other business advice. "Most of the time, Mylie just wants to be heard, not to have me fix her business problem," he said. "So I just listen." Now, when either spouse wants to make a concrete suggestion, he or she asks for permission and has to be comfortable getting "no, thanks" for an answer.

In the ideal dual-company marriage, relative size and success are unimpor­tant. Adrienne Cornelsen runs Insite Interactive, a Dallas-based company that designs websites and mobile applications. Adrienne's business is much larger than Evolving Texas, the civil-engineering firm owned by her husband, John Cornelsen. But that may change: The Cornelsens expect that at some point, Evolving will surpass Insite in sales. Whichever business is bigger, the spouses respect each other's contributions equally. "We have a 'times-four' rule in our household," Adrienne said. "My company's revenues are four times his, so when he gets a contract for $25,000, we are as thrilled as if I got awarded a $100,000 contract. Entrepreneurs have to celebrate every win."

I was surprised by how many two-company couples I spoke to are as content as the Cornelsens. I had expected to hear more tales of overwhelming stress and exhaustion, compounded by a lack of emotional succor. In my experience, entrepreneurs need someone who is less stressed--or at least differently stressed--to whom they can confide their troubles. I had assumed entrepreneur spouses would be like two overflowing vessels futilely trying to pour their excess anxiety into each other.

What I failed to account for was the deep satisfaction bred by affinity. Simply put, married entrepreneurs get each other. As my husband, Gary, built his business, I often felt as if I were watching a foreign film without subtitles. I had no idea why he did what he did; his thinking was so different from mine, it seemed incomprehensible. By contrast, when a company-owning husband fumes over losing a sale, his company-owning wife understands why he finds the experience so galling. Resentments that can build in families that shelter only one entrepreneur tend to fizzle in dual-entrepreneur families.

In many cases, married entrepreneurs share advice and strategize as equals. They form a CEO networking group of two. But even those who keep each other's companies at arm's length respect their spouses' grit and resilience. Yes, two risk-loving, overworking, superambitious adults in one marriage are a lot. But two optimistic, never-say-die adults are propitious for a happy future. "Our attitude toward our personal lives is the same one we have in business: Don't give in to the challenges," said Adrienne Cornelsen. "We just find the solution--whether our goal is to take an exotic trip or buy a house that right now seems unattainable. Our way of thinking lets us choose an exceptional life."