Relate two variables to change together

Is it possible to relate two variable to be changed together?

Example:

class foo{
public:
     std::vector<int> v1;
     std::vector<float> v2;

     //Imaginary Code here:
     void on_v2_change(){
          std::transform(begin(v2),end(v2),begin(v1),[](auto& item){ return std::round(item);});
     }
}

int main(){
    foo bar;
    bar.v2.push_back(5.7);
    //v2={5.4}
    //v1={5}
}

Is there a straightforward way to implement the previous? something like Java or C# events.