Mimi knows best

We usually spend each weekend at my moms house. She only lives 3 miles away, but to get the most time with her we usually just stay over Friday/Saturday night. So each weekend she and Coy sleep in the same room since our bed room at her house is too small for all 3 of us to fit in. Well, for the past 3 weeks she feeds him at 10 and he sleeps until 4, that is 6 hours!!! I cant believe it. He has only done this 1 time at our house. I have been doing each step that she does: 1) feed him his cereal, 2)change him, 3) swaddle him, 4) rock him while he finishes his bottle, 5) put him to bed. When I do this at home he still wakes up at 1-2 am. What am I doing wrong?