Frank J. Wilstach, comp. A Dictionary of Similes. 1916.

Inseparable

Inseparable, as a shadow to a body.
—Robert Burton

Inseparable as Athos, Porthos and Aramis.
—Fyodor Dostoyevsky

Inseparable as finger and thumb.
—George Farquhar

Inseparable as peanuts and the Bowery.
—Kate Field

Inseparable as beauty and love.
—Mrs.
—Jameson

Wheresoe’er we went, like Juno’s swans,
Still we went coupled, and inseparable.
—William Shakespeare