@annastasia First of all, what is their "adjusted age"? For example, if they were born two weeks early, their adjusted age would be 6 weeks. This is important for twins because usually they are born early and when it comes to feeding schedules and sleeping through the night, their little brains don't care when they were actually born because they won't develop any faster.
At 8 weeks (adjusted), their brains should start producing melatonin, a hormone critical for being able to regulate sleep. It's a magical milestone in which sleeping through the night is now a possibility.
So it sounds like you're getting closer to that! This is a great time to start thinking about how you're going to approach putting them to bed and establishing a good sleep schedule. Are they sleeping in their cribs or in the same room as mom and dad? Do you want them to sleep in their own rooms and when? You might be different, but it was important for us to transition them to their cribs earlier (because it gets more difficult as they get older). My hubby and I started bed time routines at 8 weeks and it took a few weeks for them to really start sleeping through the night, but eventually it gets easier and easier.
I highly recommend you start a bed time routine at a certain time at night. We did everything by a 3 or 4 hour schedule, so we picked a time that was the beginning of one of their cycles (7pm). At 7, every night like clockwork, we gave them a bath, a bottle, clean diaper, and jammies. Then we would hold and do a little bed time song or read a book, and then put them down in their cribs.
They would still wake up every 4 hours to eat. I would wake up at 11pm, 3am, and 6am to feed them. Then I would wake up automatically at 11pm, but they would still be sleeping, so I would just let them stay asleep. Eventually the 11pm feeding got totally phased out and then the 3am feeding, and they did this on their own. Now (they are 15 months) they sleep for 12 hours straight.
We decided to go with a modified "cry it out", where we started by putting them down and after three minutes of crying, we would go in and sooth them, and then leave again. Then we would wait 5 minutes, and the next time after that was 10 minutes. Usually they would fall asleep by the third visit, but if they kept crying, we checked in every ten minutes.
It's important to listen to what kind of cry they make during this time. When they actually needed something, like a diaper or if they were still hungry, that's a very different cry from "I don't like this place!" Eventually they learned to self sooth (suck their thumbs) and that's especially helpful for when they would wake up in the middle of the night. They usually just cried for a second and then popped their thumb in their mouth and fell asleep before I could even get up and walk down the hall to check on them.
Some other things I would suggest is a white noise machine (we use a box fan) and black out curtains. They will get to an age where one of their developmental milestones will keep them up if they see any lights or hear any sounds.
Sometimes it feels like something is just not working and you should give up, but eventually it clicks. Good luck! This is the hardest part of having twins (in my opinion) and you're almost out there!