Do I have enough milk for 2?

#2 was born 5 days ago and I have been supplementing with formula because he has been having trouble latching and I pump when I can since my daughter 22month old wants to all of a sudden get on my boob when she sees me pumping, she’s jealous when it comes to me putting her brother on my boob or even pumping for him. But when I do get him to latch I’m wondering if he’s getting enough because then he will chug a bottle of formula or pumped milk about 1/2hour later. I should also mention he was born at 9.8lbs 😳 so he needs more milk than the average newborn 😂 so idk if that’s why he acts like he’s starving shortly after eating.

Have any moms successfully breastfed two kids? Obviously I know it’s possible but I’d like to hear success stories from moms who have had trouble in the beginning.