2.5 year old dropped nap and now wakingear early! Help 4

[WhyTheHeckMe]

Ds is 2 and a half and has always slept really well. Bed at 7pm, asleep by 7.30pm. Then wake between 7-8am.
He napped for 1-2 hours.
However over the last 4 months his nap was getting later as he just wasnt tired
He was not falling asleep till 2.30 in the end meaning his bedtime was really late, often 9pm. If we let him nap past 3.30 it would be even later.
So we gradually dropped it apart from the 3 days he's at nursery where they manage to get him to sleep early every day (by 12.30). While he's there he never has more than 45 mins.
8 weeks ago ds2 arrived and at the same time ds1 realised after 9 months he can actually get out of his bed.
So now we are left with a son who still goes up at 7pm, spends the next 2 hours coming out of his room, then is now waking between 5-6am wide awake and is hardly sleeping in the day.
There is no difference on the nursery days when he is having a short and early nap to the days when he's not napping at all.
Please help!
My 8 week old wakes at 3am for a feed and often goes back to sleep at between 4-5am, so with my toddler then waking up for the day at this time I am feeling pretty rubbish. Finding myself getting cross with ds1 because I can't understand how he's gone from sleeping for 13/14 hours a day to more like 8-9 hours.
Help!

[SleepingInYourFlowerbed]

Could it be more to do with the arrival of his baby brother? Does he think he's missing out on something in the evening so doesn't want to stay in bed?