Hello and thank you for contacting us.
First of all, I would like to say that times have changed. 30 yrs ago, physical abuse was encouraged as a form of discipline and parents would consider this normal. In the same way sexual abuse would be encouraged to be kept as a secret and not think twice about it or discuss it openly. Thankfully years have changed and our belief systems have progressed. Now victims of sexual abuse call out the abuse and the abuser and any form of abuse is punished accordingly as there are studies to prove their damaging effect on individuals. Forgiving your brother for the sake of religion while you are still hurting inside could be very pretentious. Your parents are obviously very influenced by their religion and their perception of it, but this does not mean that you need to share these views.
In terms of your children's experience with extended family, it would have been nice if they did have the experience of getting to know grandparents and enjoyed a healthy and caring relationship with them. However, in cases where contact with grandparents proves to be damaging, it would be much better for them to keep a distance. They are not going to suffer any damage from not having this relationship and I am sure that you are compensating enough for this already. All the confidence, love and care that are receiving from you and your husband I am sure that is more than enough in order for them to be raised as mature adults, capable of forming strong and trusting relationships. They are lucky to have you!
Hope that helps
All the best