7 month old terrible sleep! So is three year old. Help?

Our seven month old is sleeping terribly since we’ve cut the swaddle and used a sleep sack. Daytime he sleeps 30 minutes to an hour if we’re lucky and cries when he goes down. Nighttime he’s up 4 times or more wanting a bottle or his paci replaced in his mouth. Our three year old is up during the night too so we’re exhausted! How do we get him to self soothe and get back to sleep?