In William Wordsworth's poem, "We are Seven," the line that is repeated in one form or another is "we are seven."
It is repeated twice as "we are seven," and once as "seven are we."
Repetition in poetry is used to stress, in this case, an idea. So that the reader does not miss the point, the poet will often repeat it.
In this poem, the little girl points out several times, when asked the number of children in her family, "we are seven." The speaker's confusion arises because two of the seven children in this family are buried in the graveyard next to the child's cottage. In his adult mind, it means they are "gone."
However, for the eight-year old child that is explaining, she sees the brother and sister she has lost as no more distant to her than her siblings at sea, and the two who now live in Conway. In this child's mind, the fact that they have passed on does not convey a sense of loss to her.
She visits with them regularly as she does her chores or sings to them...
"My stockings there I often knit,
My kerchief there I hem;
And there upon the ground I sit,
And sing a song to them.
The little girl even explains that when her sister dies, before her brother passes, they both still play where her sister rests:
"So in the church-yard she was laid;
And, when the grass was dry,
Together round her grave we played,
My brother John and I.
In essence, the adult sees these children having left their life on earth to live in heaven, but for the little girl, she is not sad as she feels the presence of her siblings just as clearly as if they were sitting next to her.