954 Hi Sergio,
This definitely sounds like it is most likely dominance aggression, especially if it is a mature rottweiler and barely has contact with the family. This would technically be considered “normal” for that situation since adult rottweilers can be dominant by default with those they do not have an established relationship with. So these cases can be complicated depending on what will be the expectations for the dog and require some legwork. Definitely not a quick fix situation. Have you watched the dominance aggression blueprint video here?: dominance aggression blueprint
That should be a good starting point that may lead to more specific questions.
If the goal is to have any stranger expected to pet the dog that may be unreasonable if owners decided to get a rottweiler instead of a golden retriever for instance.
If the goal is to have the children in the household pet the rottweiler. This may also be unreasonable and unfair to expect you, the trainer, to accomplish if the family does not normally interact with the dog. At this point for sure you need to be careful because children are at risk. I have known several rottweilers to severely injure family members over issues related to dominance so first plan is safety.