The stepfather's first two years

Give up the name first. Nobody is going to call you Dad because you married their mother, and if you angle for it you'll poison the well for years. Let them call you by your first name. Let them call you nothing at all, which is what a lot of eleven-year-olds do for about eight months, addressing you by standing in a doorway and waiting until you look up.

The name arrives on its own or it doesn't. One friend of mine got it at four years in, out of nowhere, in a car park. Another has been at it for a decade and is still Chris, and his stepdaughter asked him to walk her down the aisle. The title isn't the scoreboard.

What you're actually doing in the first two years is much less romantic. You're becoming furniture. Reliable, present, unremarkable furniture that turns up at 7:40 every weekday whether or not anyone's pleased about it.

Enforce her rules before you write any of your own

The fastest way to lose a stepchild is to arrive with a new regime. Bedtimes, screen limits, table manners, tone of voice. You've got opinions, some of them better than the ones currently in force, and you need to sit on almost all of them for a good while.

For the first year, your job is to enforce her rules, not invent yours. That means when the rule is no phones upstairs, you say "no phones upstairs" in exactly the words she uses, at exactly the volume she uses. You're the second voice on an existing policy. You're not the new management.

This does two things. It tells the child that you and their mother are one unit, which they will test relentlessly and need to be true. And it keeps you out of the trap where every instruction you give gets heard as an outsider seizing ground.

Disagreements about the rules happen after bedtime, in the kitchen, with the door shut. Never in front of them. Not once. A child who learns they can split you will spend the next six years splitting you, and they won't even enjoy it.

Then, slowly, you get to add things. Usually it starts with something physical rather than verbal. You're the one who does bikes. You're the one who does the maths homework because you're better at it than she is. Authority in a blended house is earned through competence at small specific jobs long before it's earned through any speech.

Their father isn't your competition

Say nothing about him. Not a sigh, not a raised eyebrow when he cancels, not the phrase "well, that's your dad for you."

This is harder than it sounds, because he may well behave badly and you'll be the one holding a crying nine-year-old at 6pm on a Friday when the pickup didn't happen. The urge to editorialise is enormous. Don't. The child has to work out who their father is on their own timetable, and every critical word from you delays it, because it forces them to defend him instead of see him.

What you say instead is factual and boring. "He's not coming tonight. That's rubbish. Do you want to do the chip shop or shall we do beans on toast?" Name the feeling, don't name the failure.

And if he's decent and involved, actively make room for him. Text him the fixture list. Tell him the kid scored. You lose nothing. A stepfather who competes with a living father puts the child in a vice, and the child will always, always side against the newcomer, whatever the evidence.

The exception, and it's a real one: if there's genuine danger, you stop being diplomatic and you get advice from a family solicitor and, if needed, the police. Neutrality is a strategy for ordinary disappointment, not for harm.

Logistics is the love language

Presence is measured in ordinary weekdays, not in days out. Anyone can do Alton Towers. The standing you're after comes from being the person who knows their shoe size.

Learn these things and keep them current:

• The names of their three closest friends, and which one they've currently fallen out with
• Their teachers' names
• What time training starts and where the kit bag lives
• Which foods they've gone off this month
• Their PIN-level details: reading book, spelling test day, the thing they're dreading on Thursday

Then do the unglamorous work. School run. Dentist. Standing on the touchline in horizontal rain in January with a flask, saying almost nothing, driving home with the heater on full.

Stepchildren clock effort with terrifying accuracy. They notice that you came to the Year 6 assembly and sat through forty minutes of recorder. They don't say thank you. It goes in the ledger anyway.

The line they'll test

At some point, usually during a discipline moment, you'll get: "You're not my dad."

You need an answer ready, because the improvised ones are all bad. The one that works is calm, short, and doesn't argue with the fact, because the fact is true.

"No, I'm not. I'm still not letting you speak to your mother like that."

Don't get wounded. Don't counter with everything you do for them. Don't leave the room. The child is checking whether that sentence is a magic word that makes you disappear. When it isn't, and you're still there the next morning doing the toast, something settles that no conversation could have settled.

Expect it two or three times. Expect it again at fifteen for entirely different reasons.

Money buys nothing, and you should still pay

Paying for things earns you no affection whatsoever. The forty quid boots, the school trip, the driving lessons. None of it converts. Anyone who tells you otherwise is selling something.

Pay anyway, without comment and without keeping a mental invoice, because the alternative is a household where one child is subsidised and another isn't, and children work that out in about a fortnight.

What you should sort out is the paperwork, because the law probably gives you nothing. In most cases a stepfather has no automatic parental responsibility, can't sign a medical consent form, and has no standing if the marriage ends or if you die. Make a will. Talk to your wife about what she wants to happen to the children if something happens to her. Then take the whole lot to a family solicitor and ask specifically about parental responsibility and guardianship where you live. It's a dull afternoon and it's the single most fatherly thing on this list.

The timeline, honestly

With a four-year-old, you'll feel like a father inside two years and they may have no memory of a time before you. With a fourteen-year-old, you might get five years of polite distance and a relationship that only really starts when they're twenty-three and need help moving a sofa.

Some of it never lands. There are men who did everything above for a decade and got a cordial Christmas card. That's a real outcome and you have to be able to live with it, because the moment you're doing this for the return, the child can smell it.

You'll know you've arrived when they bring you the problem first. The flat tire, the argument with a mate, the thing they haven't told their mother yet. Don't make anything of it. Get your coat and go and look at the tire.