Notes:
give yourself an hour or so of time alone to do this. Select 1 ancestor to start with (you can do others at later times) Then read this - https://sites.google.com/site/thestoiclife/the_teachers/maurcus-aurelius/meditations/01#16
and at the beginning add From my father I learned ...
Then with a pen and your journal, begin by writing.
"This is my expression of gratitude for the life of .... From him/her I learned [then write the first thing that comes to your mind.]
Explain how you felt, try to remember watching them with other people, not just you. How did they behave, how did the treat the things in their life. Even from their negative behaviour you can learn something. Like for Aunt June, I learned that a sharp and criticising tongue causes hidden pain to those who hear it, and they sometimes will not even show it. I learned that pain is not only caused by blows, but by the words that are said.
After each 'lesson' say something like, "And I am grateful, for I now know that to sew X is to reap y, and I will/will not sew x."
your honest memory is what is important here.
It will be hard, but cathartic. Be sure that you will not be disturbed, and try to have a picture with you or something that reminds you of them. even their full names written carefully on a piece of paper in front of you.