Chronic split nights (over a year now...)

[MrsKaty]

Hey all. Hoping someone on here might have been through this and have some advice. This will be long, sorry...

My LB is 2 years and 4 months old. 5 nights a week (on average), he splits his nights and is normally awake for 2-3 hours. We've been doing this since his 1st birthday. We both work and are completely beyond exhausted. Hubby and I take it in turns to be 'on' for the night.
As you can imagine, we've hauled the internet and tried everything we can. We've lengthened naps, shortened naps, dropped the nap entirely (current situation), tried early bedtimes, late bedtimes, early wake times, late wake times, no wake times. Nothing has helped.
We have a good bedtime routine and he falls asleep unaided. When he wakes, we keep it dark, keep interaction minimal. He doesn't seem to want anything, just physically can't seem to get back to sleep. And he does try, bless him. He will lay there for the whole time trying to sleep, he just doesn't seem to be able to.

His body clock seems to be stuck at 8pm for bed and he's waking up at 6:30am-ish. I realise that this is very much on the lower end of the average sleep needs for his age, but when he sleeps through on this schedule, he's very chirpy and happy all day.
He doesn't have a nap anymore because he was waking at 6:30am, wouldn't go for a nap until 12:30pm, we'd wake him at 1pm and then he wouldn't be ready to sleep until 8:30/9pm. It was just getting to the point of there not being enough hours in the day to fit it all in.

Sorry this is horrendously long. I will try anything. Thanks if you got this far.

My second is similar. She's had issues with split nights from about 6m. For 6-18m they'd be frequent - sometimes we'd have a few weeks of them being every night, followed by periods where they were maybe a couple a week. Very up and down, though on other nights she still woke 1-2 hourly so no one was getting any rest anyway. On split nights, she'd wake 1-2 hourly from say 8, with a 3 hour block awake in the middle of the night.

From 18m they have been much rarer but we still get them sometimes at 4! Now we might have a spell of 3 in a week, followed by several weeks without. It's usually something like 2-5am. That pattern has been going for years now. Essentially, if she wakes and doesn't go back within about 30m it's ALWAYS 3 hours for her.

I have zero advice, just to say hang in there, you aren't alone. Even rubbish sleepers usually eventually get better.