First of all, congrats on your new little babies!
I'm afraid that I have no advice on how to get them to go longer (mine were actually very sleepy to start with and so did manage 3-hourly for a very brief - too brief IMO - stint!) but I would say that them feeding hourly is competely normal, just vvvvv tiring. I would agree with what has been said so far in that you need to get tandem feeding sorted, that made all the difference for me. See if there is a local BF counsellor or ring one of the helplines and see if someone who lives nearby can come and help you in person.
Once I was tandem feeding, I ALWAYS fed them at the same time, especially at night. If one woke up, that was it, the other has their nappy whipped off to wake them too, and they both had a feed. Sounds cruel but it did mean that I got some decent (2-3 hour) stretches of sleep, and tbh they often both started stirring at the same time anyway.
I also did a LOT of cluster feeding, parked on the sofa from about 5ish - 9 or 10pm sometimes. I felt that nothing was coming out but it was just my DTs bulding up my supply....and a very good excuse to have my DH cook supper/massage my shoulders/bring me chocolate, etc etc.
And, I know it's hard, but do try to rest as much as poss during the day too. Even if it's not in bed, but lying in front of the TV, it's still helping you recharge your batteries.
Good luck and stick with it as when it settles down a bit it is so much easier (I imagine) that sterilising all those bottles, and it's a great way to give both your LOs a cuddle at the same time. That's the bit I still love as mine are on the go all day long. The only time they stop is for their morning BF!