XGboost with group-specific and individual-specific data
You can use all executives if you believe their compensation is governed by the same function. That is, all things equal, you expect all executives to have equal pay.
If not, perhaps you should add a feature that tells the function of each executive (CEO, CFO...).
Anyhow, the fact that part of the features is the same for multiple examples is not a problem.
It would be a problem if you had very many examples from one company and you're looking for a model that applies to all companies. If you used loads of examples of one company, your model would be biased towards the pay at that company, but since you have 5 from each company, I don't see the problem.