But defining what it means to be a good parent is undoubtedly very tricky, particularly since children respond differently to the same style of parenting.

句子主干：But defining... is undoubtedly very tricky。(主+系+表)

修饰成分：what引导宾语从句：what it means to be a good parent，其中it是形式主语，真正的主语是to be a good man。Since引导原因状语从句：particularly since children respond differently to the same style of parenting。

翻译：但界定“做好父母”的内涵无疑非常困难，尤其是因为孩子们对于相同育儿方式的反应有所不同。