Re:
So, either the ship put him a stasis sleep where he didn't age on the journey, allowing time for Martha and Jonathan to be born, grow up, fall in love, get married, and find out that they have kids before his ship arrived, or the ship was really fast and the Kents were born before him.
Unfortunately, the presence of the New Kryptonians blows up these ideas. Since Zara is approximately the same age as Clark, there is no room for time-shifting him during his trip to Earth.
Bob
