Well, there is some appalling nepotism in many companies, one example would be flight safety officer positions offered to relations of company managers, but advertised openly on company webpages not often read by aircrew.
The problem with nepotism as an issue is that individuals who benefit from it normally retain positions with better job security, more money and power over standard mortals. One company definitely used cronyism as the recruitment standard, one lucky puppy, 200 hrs flying experience with a daddy who owned a tour operator ended up with a brilliant jet job while gulf war 1 veterans and experienced type rated pilots rotted at home. Now line training and given power and economic superiority over the unfortunate. Whether this sort of behaviour is common in medicine or engineering is open for debate.