My son was four before he slept through the night the first time, my daughter was near 3. Some kids just seem to be like that.
They both woke every 2-3 hours for the first 18 months and then settled down to once or twice a night plus early rising after that.
My now 13 year old son now refuses to wake up and leave his bed. I think he's makign up for lost time. I do make a point of ensuring I wake him up early at least once at the weekend though, just out of petty vengance.
btw, my son had the privelege of beign admitted to intensive care at 12 hours old - he'd shouted/cried so much he turned blue and had to be put on oxygen. This extreme screaming did rather set the tone for the next 6 months of my life tbh