It's not easy sharing a house with OTTs. (That's Older Than Teenagers – the students who, like the undead, are stuck in the twilight of home because they can't afford to move out.)
Nothing quite fits. They go out as we go to bed. They stagger back in the morning as we get up.
We like clean crockery in the cupboards. They like it used and dirty under their beds.
But you can't afford to argue about anything, or living together would become unbearable. So you limp along in a grey zone of extreme tact.
"Does anyone else feel that the house is looking incredibly dirty?" you say.
OTT no. 1 looks puzzled. "No."
"I just wondered if..."
OTT no. 2 says kindly, "Cup of tea, Mum?"
To be fair, my one remaining teenager isn't much better. I asked her to hoover the stairs recently, and the house quivered with tension for hours.
But I forgive them everything. Because, in the past 18 months, I've written my first novel, which is about to be published. And I couldn't have done it without them.
(If you're thinking of writing a novel yourself, I recommend OTTs highly. Borrow some from a neighbour if you haven't got them yourself.)
There are disadvantages. They're not particularly helpful when you need to concentrate, because they keep bursting into the room with urgent questions that have no answer, like, 'Where's my phone?'
The house is never quiet. OTTs have loud conversations with friends in the hall. They slam the front door on their way out to yet another minimum wage, zero hours contract. They never remember to feed the kitten, who takes revenge by patting the 'x' key until the screen is filled with kisses.
But as cheerleaders, supporters and creative artists, they're brilliant.
Right at the beginning, I said to OTT no. 2 that I was thinking of writing a love story about soul mates who are meant for each other. He nodded. But there's a problem, I said. He looked marginally more interested. They never actually meet, I said. He laughed.
So I began. But before long I was floundering. I couldn't do this on my own. For weeks, as my brain became increasingly addled by a cast of characters who wouldn't behave, I fired questions at anyone who happened to be standing by the kettle.
"I want to show how safe and boring someone is," I said to my daughter.
"Make him eat fun-sized packs of Maltesers."
OTT no. 1 wandered into the kitchen. "Give me the name of a film set in New York that makes you think of a new father."
"I Am Legend?"
A few days later, I interrupted OTT no. 2 while he ate Shreddies at 4pm. (Most of the time, he seems to be two meals behind everyone else.) "Akash's father is a millionaire who lives in...?"
"Munich."
They understand plot. They know about dramatic tension. I think it comes from all those years of Grand Theft Auto.
But the best thing of all about trying to write your first novel with OTTs in the house is that they know what it's like to chase after something you really, really want when you've got little hope of getting it. Their lives are full of unattainable goals – new shoes, somewhere to live, a job. It seems perfectly normal to slog away at something with no chance of success. Mum has shut herself away to write a book that no one might buy? Cool.
They're looking forward to the launch party. I like to think it's because they're proud of me. But it might just be because of the free drink...
Marianne Kavanagh's debut novel FOR ONCE IN MY LIFE is published on May 29.
Marianne's warm, wry and witty columns for Parentdish - Surviving Teenagers