What compatibility actually means

"How do I know they suit me?" is usually answered with talk of chemistry and ease. Those are real, but they are not what a marriage rests on.

Getting along in conversation is easy. What gets tested a year into a marriage is something else entirely.

What does not decide it

Shared hobbies. Both liking travel, or reading, or the same food, is pleasant and has no bearing on whether a household holds together. Most settled couples differ here.

Initial attraction. Necessary, insufficient, and changeable.

Similar personalities. An outgoing person and a quiet one can complement each other. The problem is never a difference in temperament; it is one of you holding the other's temperament in contempt.

How quickly it felt comfortable. Sometimes that is a sign of honesty. Sometimes it is a sign that the other person is skilled at showing you what you want to see.

Six places that do decide it

1. Expectations about daily life. Where you will live and with whom, in which country. Whether she works, and whether that holds after children. This is the most common source of early conflict and the least often raised beforehand, because each side assumes their answer is the obvious one.

2. Religious practice as lived, not as stated. The gap between two people who both describe themselves as practising can be enormous in practice. More dangerous still is entering on the hope that the other will change afterwards. That bet usually loses.

3. Money. Not the size of the income — the attitude to it. Saving and spending, debt, obligations to parents, who decides on a large purchase. Two people on identical incomes with different attitudes here will argue more than most.

4. Boundaries with parents. How present will they be? How much say do they have? And who has the final word when your wife and your mother disagree? A heavy question, and postponing it does not remove it.

5. Children. Do you want them, when, and who does the practical work in the early years? How will you raise them, in faith and in language? And the hardest one: what if conception is delayed?

6. How you disagree. This is the most important of the six and the least amenable to a direct question. What does each of you do when angry — go silent for a week, raise your voice, call your family, apologise quickly and then repeat it?

You will not learn that from conversation. You learn it from the first small genuine disagreement — which is why several meetings before the contract are worth more than one long pleasant exchange.

How to test it in practice

• Ask the six directly, spread across meetings, and answer them yourself with the same honesty.
• Watch for consistency. Do they say the same thing the third time? In front of their family?
• Create one small real disagreement, not a manufactured one: object to something, change a plan, and watch what happens.
• Ask people who know them. Their family, colleagues if you can. People describe each other more truthfully than they describe themselves.
• Notice what is not said. A subject that is always avoided is not forgotten.

The largest warning sign

A disagreement treated with "we'll sort it out after the wedding."

Marriage does not resolve an existing disagreement; it magnifies it, because it adds shared housing, shared money and two families. Whatever you have not agreed on before the contract, you will not agree on after it.

Finally

Compatibility is not sameness. It is that your differences sit in places life can absorb, and your agreement sits in the places it cannot.

Which is why matching on photographs and hobbies does not work. At Mizan the filters are built on country, age, religious practice and way of life, because those are closer to what actually decides it. The rest takes meetings, families and time — and no algorithm produces it.