daughter-in-law

My daughter-in-law is most likely suffering from PPD. My son has cut off all relationships with us because we don't love the daughter-in-law enough. Every molehill is a mountain. No one in our entire family is allowed their friendship. My husband and I beat ourselves up over this for a long time but now believe that no matter what we would have done, it would have turned out the same.

I read in one of the post that a man went out with a girl that suffered from PPD because it made him feel more worthy to help someone in need. I truly believe that my son did the same thing and he often dated girls with mental problems.

We are trying to get a cell phone number for my son at this point. My sister, a therapist, feels that an intervention may help him see that this is an abusive relationship and not healthy for him or his daughter who is 4. I just can't see him leaving her because of the child. It's all very sad. Last year we call to see if we could take our granddaughter out for lunch, and we got a terrible letter from our son wondering why we wanted to take her out and what did we want to fill her head with. My daughter-in-laws parents died about 2 years ago and that little girl has no grandparents now. We don't call, all phone calls go to the answering machine, we don't email---they never sign the email so you don't know who you are talking to.

Does anyone have any ideas how we can get our son and grandaughter back?