In her sixth grade class, half the kids were the youngest in their families, the other half the oldest. The difference between the kids has been noticeable. The youngest kids, raised by mainly silent era parents, didn't screw up too badly, The other group floated from job to job, relationship to relationship, and generally messed up pretty badly. Some have turned themselves around, but they're still not at the same place as the youngest kids are now.
The oldest kids came from more affluent families due to fewer kids; 1 or 2 compared with four or more. The oldest kids were cooler socially and fashion wise at an earlier age.
I found it interesting that the school with 4 classes for each grade would do this social experiment in 1 class in 1980. The two groups made friendships along these lines, too. I think the youngest kids had more in common with each other than with they had with the oldest kids, and vice-versa. I think the values of the parents had more impact than the year of their birth. More of the oldest kids had divorced parents than the other group.