My personal opinion is that it's up to your WH to suck it up, get in touch with his son, and let him know the pain that he and his wife's treatment of you is causing. That you are the INNOCENT party in this deception, and to spew hatred and alienate your granddaughter from you is no different than stoning to death a raped woman. You WH needs to man up and step up to defend you and frankly, my opinion is the same for your son. (((hugs)))
D-Day, June 10, 2012
What did your DIL say in the letter? Maybe more details here will elicit more helpful comments.
I agree that it is your WHs mess to clean up.
Perhaps you (or others in these shoes we wear) are triggers for other BSs that have rugswept. Maybe she is a BW too?
A good article to read about the pain of finding out later: google:
Rick Reynolds, The High Price of Forgiveness, at the affair recovery site.
it maybe something to share.
sorry for your pain and disappointment.