用逗号隔开介词结构是什么成分（同位语？插入语？）

We both came from hard-working families, of modestmeans but with strong work ethics.

用逗号隔开介词结构是是什么成分？同位语？插入语？麻烦老师解说一下？

We both came from hard-working families, of modest means but with strong work ethics.

【翻译】大家两个都是来自勤劳的家庭，收入虽然不高，但都有非常强的职业道德。

1. of modest means 和 with strong work ethics，两个介词短语都是familiies 的定语。families后有逗号，说明是非限制性定语。

2. but 表示转折对比关系：收入虽不高（中等收入水平），但有非常强的职业道德。