Age wise, yes they are quite close.
In terms of music, the first 3 were at their prime in late 70s. Their music belongs to the era of 琼瑶 works with 刘家昌 music... movies acted by 秦汉,林青霞。The next 2 started in early 80s but did not become that popular till late 80s, the music were of different genre... I would consider them as belonging to the era of 张清芳 and 郑怡