When my twins were 3, they had just dropped their afternoon nap, and as a result were going to bed quite early. They were usually asleep by 7, and would sleep until between 6 and 7 the next morning. DS3, on the other hand, stays up really late - though he just turned 3 a couple of weeks ago. I know it's because he wants to play with his brothers, who are now 6. They are supposed to go to bed at 8, but are usually awake reading or playing quietly in their room until close to 9. DS3 has been staying up that late too, and I feel like he needs more sleep. He usually does sleep a little longer - maybe until 7:30 - but this morning he was up and ready to go at 6:30, which meant he only got about 9 hours sleep or so. He does nap during the day once in a while, but he stays up late even on the days he doesn't nap.
How much do your 3 year olds sleep? Do you find that the sleep patterns of your younger children are completely different from your first born?