What ABibleStudent said about helping others think (and reason) critically instead of telling them what you have found or believe.
Most especially those family members you'd rather not lose...
Always ask, never tell...
Always try to use "objective language".
Never attack or touch their idols (GB, FDS, Watchtower, ruling religious clergy class and hierarchy).
It may also be important to know or find out what is important to a particular family member to help you choose your question.
"What is the gospel in one word?" was the clincher for me on so many levels, and led to a voluntary full-on transformation in my thinking and beliefs. The integration, wholeness and clarity that followed is indescribable...
Now I love simple, short but profound questions.
"Is legalism apostasy?" (Impossible to answer correctly unless one is very clear on what these two words really mean)
"Is moralism apostasy?" (The same as above)
"Is the word faithS scriptural?" (The word never appears in scripture which instead speaks of only "one faith". Doctrinal beliefs, which the Watchtower holds out as faith, is not a fruit of the Holy Spirit, but rather something that emanates from man.)
"What is a prophet in one word?" (No, it is not a foreteller)
"What is a prophecy in one word?" (No, it is not a prediction)