My 3 year old comes into my room and wakes up my 8 month old: Advice?

I still co-sleep with my nearly three-year-old. I get him to sleep with me and put him in his own bed when he falls asleep, but he wakes during the night and runs into my bed, usually when I’m asleep. Also, my 8-month-old is a very light sleeper and sometimes wakes 4 5 times and only sleeps properly when he’s lying on me. Im exhausted and feel like the same thing is going to start happening. Any tips?