The term "First Daughter" was not used in the 1960s, although the President's wife was called the First Lady.
Caroline Kennedy was the presidential daughter during the early 1960s - until her father, John Kennedy was assassinated in November 1963. After that Luci Baines Johnson was the daughter of President Lyndon Baines Johnson until Johnson's term of office ended in January 1969. For the remainder of the 1960s, the presidential daughter was Tricia Nixon, daughter of Richard M. Nixon.
Jesse James
Your daughter and your nephew are first cousins. His daughter is your daughter's first cousin, once removed.
Your daughter and your nephew are first cousins. His daughter is your daughter's first cousin, once removed.
Your niece and your daughter are first cousins. Your niece's daughter and your daughter are first cousins, once removed.
1960s
1960s
You mother's sister is your aunt. Your aunt's daughter is your first cousin. Your first cousin's daughter is your first cousin, once removed. So your mother's sister's daughter's daughter is your first cousins, once removed.
1960s somewhere round the 1960s check on wikipedia for the actual date.
If your daughter is also your wife's daughter, your daughter and your wife's first cousin are first cousins, once removed, otherwise they are not related.
Your niece and your daughter are first cousins. Your daughter and the daughter of your niece are first Cousins, once removed.
Your nephew is your daughter's first cousin. So your daughter's daughter (your granddaughter and your nephew are first cousins, once removed.
The children of siblings are first cousins, so your daughter and your brother's daughter are first cousins to each other.