"Like 優しい, the na-adjective 親切(しんせつ) means “kind,” and it is used to evaluate someone who does something kind for a person in trouble or is considerate to others. However, 親切 is used to describe the character of someone based on his/her action, and is not usually used when referring to one’s own family or close friends. " source
Why 親切 is incompatible with "describing the character of someone based on his/her action" when referring to one’s own family or close friends ?
