You're right, ML. Clark was born in 1966 (February 28 - he gives his birthday in Never on Sunday). Lois was born in 1967 (I think there's a reference to her as 26 in the Pilot, and in Tempus Anyone? she sees her tombstone with the dates).
And Dean (1966, just like Clark
) is younger than Teri (1964).
Kathy