Those of us who have raised children have generally accepted the conventional wisdom that sternly informs us that when something goes wrong in a child's life, we are to blame. How many parents have spent lives feeling remorse for the roads their children have taken?

Now, however, Judith Rich Harris has come along to assure us that peers matter more than parents. While child development has centered on understanding children through their parents, it is now apparent (to her, anyway) that half of behavior is attributable to heredity and the other half - take a deep breath - to environment. In a new book "The Nurture Assumption," Harris expounds on her theory and supports her findings with independent studies.A couple of today's letters deal with families anxious to raise the children of their children because they are concerned about the ways their own children would influence their grandchildren.

Dear Lois: Sometimes good parents have kids who go down the wrong road no matter how we steer them. I have six children. I would, however, jump at the chance to get my 6-year-old grandson with me. My son is divorced from the mother, and she has done everything to keep me from seeing him. She is trying to get his visitation taken away and have her fourth husband adopt my grandson.

- Parenting Grandmother

Dear PG: You didn't mention where your son is in all this mess. Is he fighting for custody? As a grandparent, you certainly sound as if you are in a position to give your grandson lots of companionship in a household where he'd be welcome, but you didn't mention your son's attitude.

Dear Lois: We have raised our 8-year-old granddaughter ever since she was born. Our daughter is an abusive mother to her two boys, who were born after she and her husband were married.

We have legal guardianship of our granddaughter. What I want to know is how hard it would be for us to adopt her legally. I am 45; my husband is 50 and has had two major heart attacks. We do not want our daughter ever to have the chance to raise this child. Can you help?

- Kathy

Dear Kathy: Since you have legal guardianship, you should consult an attorney about the possibilities for adoption in your state. Since you are the grandparents of the child and have raised her all her life, it would seem that usual age considerations for adoptive parents would not apply. However, every state handles this kind of question differently.