This is not a habit that needs "breaking" necessarily. Babies have very different sleep cycles from adults and older children, and it is common for them to wake up during the night even into toddlerhood. Some babies who have been sleeping through suddenly start waking up. It is a normal part of development.
You don't have to interact with them or feed them when they do this. Just go in, quietly pat them on the back and leave. Find a book on babies sleep that fits with your parenting style and see what works for you (I am a fan of the Dr. Ferber, but there are many out there.)
However, I would consider pushing his bedtime back as another poster suggested. The more sleep they get, the better. Generally kids sleep better if they go down between 7 and 8 pm (give or take a little depending on the child). If you get much past this time, they get over-tired and then don't sleep as well.
Good luck!