Were they premature or full term? That might determine their typical A time if they were more than a few weeks early.
I would try to gradually increase their A times in the morning. It sounds like they are almost using that first nap as an extension to their night sleep and then by the second nap they are Undertired and so don't take a full nap. They probably can't get tired enough again to take the cat nap before BT but then end up really overtired and have lots of NWs. Then the disturbed night means they can't manage a full A time in the morning and the cycle begins again.
They are approaching the age when they will not need a third nap soon so you may just need to redistribute their two naps more evenly throughout the day.
All about the 3-2 transition- 5/6 monthsYou can increase A times by 10-15 mins every few days to give them a chance to adjust. Sometimes at this age they can show tired signs when they are used to sleeping or when they really just need a change of scene.
Typical A time for a 5.5-6mo is 2.5-3hrs.
Average A times- BOOKMARK ME! How many times are they waking at night? Do you feed every time? It can be usual to have 1-3 NFs at this age (especially for twins sharing the milk I imagine
). What time is BT and what time do you start the day?
How do they fall asleep at bedtime? Can they settle themselves to sleep in their crib or do you think maybe they are waking at night and looking for you because they don't know how to self-settle?
And well done on breast feeding twins so successfully
I'm a twin and it is great