Right, this is me being extremely honest here.
I am similar to your DP. Anything before 10am, and I can't cope. I have no real memories of anything I have done before 10am, my DC's avoid me in the mornings because I yell and am extremely moody (so they tell me).
On a school day, I have to get up at 6.45am. I don't do too well with it. I sit in the kitchen on MN quietly on my phone, with a fag and a coffee.
The older 3 DC's get ready mostly without bothering me, and DD and the DS's keep an eye on DS3 until 7.45am, when I can cope slightly better.
It embarrasses me how badly I cope in the mornings, but I manage to get everyone fed, washed and clothed and to school on time without incidents of shouting and extremely odd behaviour from me ONLY if I am given that time to wake gently.
I am trying to save up for one of those gentle light alarm clocks, because my GP has just pooh-pooed my issues with sleep.
As a bit of background, my Mother, my Dbro and my Maternal Granddad and Maternal Great Uncle are all the same.
Not one of us can EVER get up before 10am reasonably. None of us can EVER get to sleep before 1am on a GOOD night.
We are all nasty bastards in the morning, before 10am, but really gentle, caring people after then.
We have all worked evenings / Nights best, and have all really struggled with 'regular' 9-5 jobs.
My bedtime is usually between 2-3am, but has crept slightly later at present, to 3-4am.
It's horrible, I wish I could change it, tried sleeping pills around 13 years ago from a different GP. Didn't do a thing, I still felt tired at the same time (2-3am), didn't fall asleep till then, and then felt 'hungover' for most of the following day. Which wasn't appropriate with a young DC to look after.
I can't get my current GP to take me seriously.
It seems to me that my 'circadian rhythm' is out of whack to GMT and BST. Though I DO fare slightly better every year as soon as we switch to BST.
I need to move somewhere where 2am in England works out to 11pm in that country!
I would get him to push for a referral for a sleep study (like I'm trying to.)
My DD and DS1 are the same too. DS1 especially, and he is having real issues with sleep deprivation on a school day. He goes to bed at 9.30pm (he's nearly 11, and it's the time that works best for our family.)
There are many nights where he is still lying on his bed awake at 2am, having laid there doing nothing but counting sheep and inspecting the ceiling since 9.30pm.
He had even tried counting up to 1000, then counting backwards again from 1000 to zero. He got through it THREE full times forwards and backwards before he gave up.
It really frustrates us all that our body clock seems set totally differently to the rest of the UK!
My DS2 and DS3 are far more like their Father, and are early to rise all the time.