My oldest grandson had this problem. His doctor said that little boys have more problems with this because the nerves don't mature for them. I wished we had heard about the chiroprator, we would have tried it. What the Dr had my daughter do is have him take metamusil, to help him completely empty his bowels and calcium. When he did this, it seemed to help a lot. I'm sorry for your sil, losing the trust of your son is an awful loss. Hope he catches on soon enough.