depends on what time the 3 year old gets up in the morning, our 4year old goes to bed around 7pm, when she was 3 she went to bed similar time,maybe a bit earlier like say 6:30pm, She is mainly up about 7am
Mine went about 7 -7.30ish and were always up about 6.30ish as that suited our routine. Not all families are the same though and not all kids seem to need the same amount of sleep - also depends on whether the 3 year old still has a nap.