辈 is a phono-semantic character. In the seal script, 辈 = (非) + (車). 車 acts as semantic component and 非 phonetic.
The original meaning of 辈 was extended to:
1. people of a certain kind, e.g. 我辈 people like me; 无能之辈 incompetent people
2. generation, e.g. 老一辈 older generation; 他们同辈 They are of the same generation; 老前辈 one’s elder; 晚辈 younger generation; 祖辈 ancestors
3. lifetime → 辈子, e.g. 后/前半辈子 second/first half of one’s life