According to the Princeton Profiles, the children and step-children of University undergraduate and graduate alumni have constituted between 10 and 15 percent of the enrolled classes at the University since the Class of 2000…
The acceptance rate for alumni children and step-children has wavered without a specific trend between 35 and 42 percent since the Class of 2000, with the Class of 2018 hitting a record low of 30.8 percent, according to the Princeton Profiles…
[Dean of Admission Janet] Rapelye said undergraduate and graduate alumni ties were given equal weight. She added that other familial relationships, such as that of University grandparents and siblings, are also noted but not added to the statistics in the Princeton Profiles.
“We are aware of a sibling on campus or a sibling who has gone to Princeton,” Rapelye said. “But the sibling who is applying needs to be able to stand on their own.”
If you’re interested in how the math shakes out, here’s the stats for the most recent round of admissions.
Princeton
Duke-Trinity
Any university with an admit rate below 15% or so can be pretty unpredictable; students on CC are always shocked in the spring to see someone get into Harvard but not Cornell. He should apply early to the one he likes better; trying to game the system is pointless here. He has a solid shot at Princeton with his stats and sibling bump, IMO.