T.M.
I have 2 kids and it seems that the culprit for that is always the afternoon nap. My now 6 year old took naps until he was a little past 3 yrs old but then at night he wouldn't fall asleep until 10 - we took away his nap and he was back to normal, going to sleep at his normal bedtime. It is an adjustment (mostly for moms) when you take that nap away but the kids seem to do fine. My now 2 1/2 yr old has done away w/ her afternoon naps (on her own) and falls asleep by 7:30 pm each night. Each kid is different and require different amount of sleep. You might try a few days w/o the nap and see what happens. Good luck.