I’ve sat with far too many women and men heartbroken by marital infidelity. They wonder what signs they missed, what they could have done differently, what anyone could possibly do to prevent such a thing. Should they have noticed their husbands laughing more brightly than usual at someone else’s joke? Should they have spoken up and insisted their wife not go to that team-building day away from the office, knowing that Eric from sales—who also happens to be the local Cross-fit champion—would be there?

The underlying question is this: is it safe for married men and women to have friendships? Or, as Harry says in When Harry Met Sally, are we to conclude that “men and women can’t be friends, because the sex part always gets in the way”? Many have concluded that with the risks of sexual unfaithfulness being what they are, it’s better not to “tempt fate”. Men and women can’t just be friends, we’re told. And even if that can, they shouldn’t because it’s just too risky. Our rules function like caution tape: Just don’t even go there.

The problem with this advice, though, is that while it means well (in its goal to avoid sin), it is advice predicated on fear. And developing any set of rules based on what could go wrong isn’t the right place to start. The right place to start is with the big picture of what’s at stake and what our guiding values are, and once we’re clear on first principles, we can tease out the implications for harder cases.

This start-with-first principles method was how Jesus modeled ethics. Jesus said all  the law and prophets rest on two essential commandments: to love God, and to love our neighbors as ourselves (Matthew 22:37-40). Everything else flows from that.

If we approach the ethics of male-female friendships by working our way back from worst-case scenarios, we are starting with the wrong questions. Jesus himself didn’t withdraw from intimate friendships for the fear of sexual chemistry gone awry. If our primary question is, “How can we avoid sexual sin?”, we are framing the whole conversation around avoidance and fear.

But God has given us a framework—his first principles—to start with a better question. If we ask instead, “how can men and women live in relationship as God intended?”, we are better able to find our bearings and chart a path forward. The answer to this, in fact, is resoundingly clear throughout the New Testament: God intends for us to live as brothers and sisters in his family. Our nuclear families (the ones we’re born into or we marry into) along with the bigger family of God provide both a matrix for us to consider how we can relate, and a strong foundation for navigating the trickier questions as they come. Central to the challenge, then, is figuring out how a “big family” mindset can help us find our bearings for the everyday friendships with men and women around us.

Friendship is how we describe relationships of affinity, connection, and care from among the broader community of people we know. Friendship chooses from among acquaintances and invests more deeply and more personally. We recognize in a friend something that sparks interest, delight, or recognition. We might share a passion (for graphic novels, or ice hockey, or kayaking), or a season of life (raise your hand if you’ve made a friend during a finals’ study session, or on the sidelines of a youth soccer match). We might find friends among those who share a mutual goal—such as training for a marathon—or among a set of work colleagues who all need to survive a ridiculous boss (Michael Scott in The Office, anyone?) We find a friend when we notice that someone isn’t just one face among a sea of acquaintances, but a person of particular interest: an ally, or a buddy.

Anyone can experience both friendship and family, but those who share a common faith in Christ have a spiritual connection that fundamentally shapes their experiences. Being united to Jesus ripples into every sphere of life and affects every circle of relationships. Our primary matrix for relating to other Christians is no longer figuring out whether they’re “acquaintances” or “friends”, but already knowing they are brothers and sisters because we share the same Father (John 1:12). The kindred spirits we look for in friendship draw from a deeper existing connection: kinship. So, when it comes to how believers should treat male and female friends, we have our first principles: treat them as brothers and sisters.

1 Timothy 5:1-2 gives us our foundational framework for healthy relationships across gender lines: “Treat younger men as brothers, older women as mothers, and younger women as sisters, with absolute purity.” (NIV) As believers in Christ, we are called to have relationships with both men and women—but our controlling ethos is to make sure these remain brother- and sister-like in their tone and purity. So, for Maria considering whether she can be friends with James, the question is not “Should I have this friend or not?”, since friend is not a helpful category for discernment. A question that would help Maria better is, “are James and I behaving as siblings would?”

Friends who are functioning like healthy adult brothers and sisters have one distinguishing trait: they aren’t just a friend to their friend. They’re a friend to their friend’s marriage. Good friends should be cheerleaders for our marriages, not competitors (or predators!) to them. Friendships characterized by the integrity, communication, and community that healthy siblings have can and should be a feature of our communities. I can think of a dozen examples of friendships with brothers and sisters who support my marriage. And yes, some of the best of these I’m honored to call ‘friend’.

Bronwyn Lea is the author of Beyond Awkward Side Hugs: Living as Brothers and Sisters in a Sex-Crazed World. She and her husband are from South Africa, but now live in Northern California, where they and their three kids count their church community as family. Bronwyn serves on the pastoral team at her church and is the editorial curator for Propel Sophia, an online wisdom resource for women. Sign up for her monthly-ish newsletter here, and connect on Facebook, Instagram, and Twitter.