Routine help....please!! (twins)

Hi ladies,I'm really hoping you can help. The boys are now 5 1/2 weeks old and we just can't get a routine. They both feed every 3 hours still,but at different times (we tried forcing the other awake etc but no joy),they are really good in the day,they have their milk,play for an hour then go to sleep in their bouncers. But.....as soon as we do the "last feed" (around 7pm ish) and put their sleeping bags on in the cot they start. 90% of the time at night they want to play after feeds and refuse to go back to sleep. We've tried everything and I refuse to actually let them play at 4am so I don't know what to do! Me and hubby are soooo tired,we've lived on 3 hours sleep a night or less since they were born and we spend every night ateach others throats because we're shattered. We can't even catch up with sleep in the day as we have 2 older ones. Any ideas please girls?

A v frazzled K and boys! x