If child has nf1 and parents are negative, but were told it could be in reproductive cells, is it possible for 2nd child to not have it, but 3rd does?

New mutation?: If neither parent carries a mutation for NF (neurofibromatosis), then the affected child is a new mutation. Each future child has a very rare risk of having a separate new mutation causing NF. Realize that every child in the world has a rare chance of getting a new mutation causing NF. No worries... unless one's geneticist feels there is a reason to worry. If so, the geneticist can evaluate more.