I have 15months twins... and a 2 1/2 yr old toddler.
Seriously, I went thru this until the twins hit 1 yr.
Around 9months, I reached out everywhere to find out how to get these cuties to sleep all night.
If the babies gain weight and progress normally, there is no reason they can't sleep 10 hours, or more. At 1y old, my twins finally started sleeping 12 hours .. 7pm-7am...
I also fed them oatmeal or rice cereal at night to help keep them full.
I followed the advice from my pediatrician.... he said to comfort the baby when he/she wakes up,, but no food.. put them back to bed.
Then go back in 5 minutes if they are still crying.
Comfort them again, and leave them again without a feeding.
then go back in 10 minutes.. then 20, then 40.
The point is to let the babies know you are there for them... BUT also they have to learn they are not getting food in the middle of the night.
This is, at least partially, from some baby book.. but I forgot the name of the book because I never bought it.
For my older toddler, this worked in 2 days, back when he was 3 months old.
For my twins, I first had to separate them into two separate bedrooms.. Then, one baby(girl) was sleeping until 4am in a couple of days.... but it wasn't consistent. My other twin (boy) took a week before he slept thru the night for the first time..wihout any wakeup.
I will say this process reduced the stress on mom and dad within a week... and was the light of hope at that time. It still took a few weeks to get things in decent sleep patterns.
My twins still didn't sleep great until 1 yr, but my toddler was getting up and crying in the hallway. I think he was waking up the babies sometimes, so it's hard to be sure how long the process really took ...
Don't wait... good luck!!