To be fair, I dont know why you guys are looking so deep into familial conections. As alot of you have mentioned, these complex relationships have changed considerably in the last century. However, you are failing to appreciate another back door that has emerged. Funding, particularly government, NGO and corporate.
The top 100 universities in the world have so much external funding that the nepotistic relationships have inevitably chnaged and expanded. Its no longer just the case...where did mummy and daddy go but essentially an issue now of 'money talks' especially at post graduate levels of education and in the Ivy league