Am I nagging?

This.

Not nagging, they are his kids too. Where is your downtime or chill time.
Harsh but he needs to step up,

Your statements are completely contradictory. How can he be a great dad and partner but also want f all to do with any of you?

People who want to be in relationships with a partner or children or whoever put the time and effort in to nurture those relationships.

Being a stay at home mum means you are “working” the hours that he works. When he clocks off from his job, so do you and from then you are just two parents equally looking after your children and home.

There's no such thing as 'as good as' married when one person has chosen to be dependent. You don't have any legal protection.
Are you on the deeds of the house? Is the misogynist paying towards your pension?

https://www.citizensadvice.org.uk/family/living-together-marriage-and-civil-partnership/living-together-and-marriage-legal-differences/

Genuinely don't see how being the one who works equates to doing little else at home, especially with kids.

In terms of pure "hours", he does what - 10 hours a day at work - while you do the corresponding 10 at home. That leaves about 4-6 hours where you're both home and awake. Why does he get them free while you carry on working?

In terms of being a good father, does he think his kids will simply understand his rationale? I.e. That because he works, he doesn't need to bother with them as much?

Being a good dad isn't about taking them for days out. It's about being present - day on day - for the more mundane parts of daily life - teatime, bedtime, and the times around it.

he will come home from work spend some time downstairs with us and then he will go upstairs , lay in bed/on the bed watching tv, enjoying his own company. Sometimes he will even eat dinner up there. When he’s off work, he pretty much does the same.

he’s a great dad always there for his kids

Huh?????????

No he isn't!!! He is an absolutely terrible father and a piss poor role model to his kids!!! What type of parent lies in bed watching TV and eating their meals whilst their children are downstairs?!

or he makes an excuse to sleep downstairs most of the time 🤷🏻‍♀️

So he comes in from work, buggers off upstairs to bed (where he eats his meals too?!), then when you go to bed, he goes downstairs and sleeps down there? Unless he wants sex I presume?

Wow. Please tell me you don't take his meals up to the bedroom for him....

Who owns the house OP? “We” didn’t do anything if the house is only in one person’s name if you’re not married.

When my DC were small, DH was the stay at home parent. I have a short commute, which I thought of as my downtime. When I got home from work, I got stuck in with family life. After DC were in bed, I enjoyed chilling out together with DH. I can't imagine a scenario where I'd have opted out of family life in this way. It's selfish and it's disrespectful to you.

How did family life evolve? Was there a discussion around having children and what life might look like? Has he always been like this?

You are simply another domestic appliance op, with a vagina.
He has checked out, he can't even sleep in the same bed as you and you aren't married?
How long have you left yourself vulnerable like this, the whole 12yrs?
I'd get back to work ASAP because this relationship is dead in the water isn't it.

OP. He doesn’t clean anything “for you” - it’s his kids/house/life too!
It is also not “fine” that you don’t get a chance to rest when you are sick.
I think you might need to focus on your own thought processes first, then work on him.
I had to train my DH up. It took some time. “Do you want to do bedtime with child A or child B tonight”?
“do you want to do bath time or clean the kitchen (including scrubbing pots and wiping sides etc - none of this loading the dishwasher and sodding off to sit on your arse BS)
and on and on.
Sort of like asking a toddler if he wants his shoes or coat on first. Basically the world in which he lazes around like a Lady of the Manor while I run around like fucking Cinderella doesn’t exist and I told him just that.
Now I don’t need to tell him anything, he just does it. Just as well, as I wasn’t prepared to spend my one and only turn on this earth as a skivvy.

Spot on!!!

He sounds checked out of family life and its not acceptable. Sure he might need a bit of time to decompress but what about you. He's taking the piss.

Tbh I’m that person but I didn’t realise til after I had my kids. Turns out my exh is also someone who loves being alone.

The fair thing would of course have been to make sure we had equal alone time as well as some time all together. He of course thought he was entitled to all of it whilst I slogged on. That’s one reason why he’s an ex!

I of course love spending time with my kids as well, but I need some alone time to function. Getting divorced was brilliant as it forced the sharing (up to a point, exh decided that Covid lockdowns were definitely times when he couldn’t be expected to do anything… 🤔).

But just to be ultra clear, my kids didn’t get deprived of company or neglected because I made sure I made the effort - and I do love their company too - just because I know someone will choose to misread.

Now mine are old enough that they also crave alone time so we rub along very nicely, all having some quiet time and some time together.

This. I am that person therefore I didn't have kids!

He's not a husband, and doesn't parent.
OP needs to get financial security and forget this pointless man.

He sounds like a selfish manchild who doesn't care about family life. Why do you bend over backwards for him when you know it'll never be reciprocated? I suppose the thing to weigh up is whether this is really what you want for the rest of your life. He's a husband and dad in name only.

ETA - he's obviously one of those men that thinks, because he's working and financing the house and you're a SAHM, you are there to serve him as he's effectively 'paying your wages.' Urgh!

I can’t believe he even had the audacity to tell you you wouldn’t be allowed to rest like he had if you were ill - without it even having happened! He’s just saying “you’re less of a person than I am btw”.

This!

He’s not just “enjoying his own company”, he’s ducking out of the shared work of looking after the children. This isn’t something he gets to do as a parent.

The default during time when neither of you are out at work is that you’re both responsible for looking after the children. Anything else has to be negotiated.

If he wants to spend time alone whilst the kids are in the house, you need to get equal time to just go and “chill” whilst he parents solo, and then you need to arrange time to be all together. He doesn’t get to just melt away when he feels like it.

Also, “nagging” is a misogynistic term when used in this way.

SAHM, 'traditional', but doesn't sound like you're married? So just another skivvy putting herself in an extremely vulnerable position for a man that doesn't respect or appreciate it?

Why do women continue to do this to themselves? It's so bloody depressing.

I can understand that he might relax for 20 minutes of an evening after work. Then you should be able to relax for a similar time. Go up and swap with him or join him?

Both help to get the children ready for bed, clean their teeth etc. read stories and then both go upstairs.
Are the children going to bed too late?