Sonnet 31 expands upon the sentiment conveyed in the preceding sonnet's concluding couplet, "But if the while I think on thee, dear friend, / All losses are restored and sorrows end." In the present sonnet, the young man is a microcosm representing all the poet's past lovers and friends; however, the poet's separation from the youth also represents the loss of companionship with these now-dead lovers and friends. Ironically, the young man, whom the poet earlier admonished to bear children to stave off death and mortality, now himself becomes an image of death: "Thou art the grave where buried love doth live."
The sonnet demonstrates that the poet is really writing to himself rather than to the young man. His physical separation from the youth prompts him to remember lost loves and then link them to his current relationship with the youth. The poet rejoices that his dead friends are metaphysically implanted in the youth's bosom, but lost friends and lovers — not the young man — are the main subjects of the sonnet.