This is not always--though nearly always--the case.
The double-period in music finds its poetic analogy in almost any stanza of four fairly long lines, that being a design in which we expect unity of meaning throughout, the progressive evolution of one continuous thought, uniformity of metric structure (mostly in _alternate_ lines), the corroboration of rhyme, and, at the same time, some degree and kind of contrast,--as in the following stanza of Tennyson's: Phrase 1.

"The splendor falls on castle walls, Phrase 2.

And snowy summits old in story; Phrase 3.

The long light shakes across the lakes, Phrase 4.

And the wild cataract leaps in glory." The analogy is not complete; one is not likely to find, anywhere, absolute parallelism between music and poetry; but it is near enough to elucidate the musical purpose and character of the double-period.