The Harvard Crimson presented the results of a survey to which about 60% of the freshman class had responded, and it indicated that only 63.2% of the respondents said they had no family connection with alumni or current students at Harvard College. Unless the Crimson was lying, or grossly misrepresenting its survey, that should count as a fact.
The survey’s number for relationships that Harvard counts when it reports on legacy admissions was margin-of-error consistent with what Harvard usually reports about legacies: 14.5% (in the survey) vs. 12-14% or “less than 15%.”