I know how hard it is.
I just tried to balance the urgency of their need. It's easy to often put the newborn first so I tried to make a point of sometimes putting my eldest first.
If my littlest one was tired that came first because once he was alseep I could spend more quality time with my older one.
After a while I got better at juggling them - I could BF one while feeding the other or lie down and put them both to sleep at the same time.
You're doing a fab job and it will get easier.