WASHINGTON – Stepping inside Kathleen Kennedy Townsend’s sun-filled apartment is like stepping into American history.

A letter from her father Robert F. Kennedy hangs in the hallway.

"Dear Kathleen, as the oldest of the Kennedy grandchildren you have a special responsibility: Be kind to others and work for your country,” RFK wrote his 12-year-old daughter, two days after the assassination of his brother, President John F. Kennedy, in 1963.

For members of the Kennedy clan, that sense of responsibility is being tested by one of their own: Health Secretary Robert F. Kennedy Jr., Townsend's younger brother and a top member of President Donald Trump’s administration.

More: Senate confirms Robert F. Kennedy Jr. as Secretary of Health and Human Services