Meaning of 子は鎹(こはかすがい) in Japanese

Examples of 子は鎹, こはかすがい in a sentence

• 最近、周りでも離婚が多いようだけど、子は鎹って事は、今は昔となったのかね。

  Lately I see a lot of parents getting divorced. I wonder if the idea of kids being a bond between their parents is just a thing of the past.