The poem alludes to Sir Thomas Wyatt, who brought the Petrarchan sonnet to England, and who was said to have loved Lady Anne, before and after her disastrous marriage to Henry Tudor. The poem implies that Wyatt was not the only poet to have loved her; but, overall, somewhat less successful in his effect upon her life.
The plural, possessive "sires'" alludes to both Anne's father and the king---for both of them used her badly and unfairly for their respective lusts (for power and sensual pleasure, respectively).
In the triple epithet describing her feet, the third adjective is obvious; the first suggests her domestic faithfulness, the second her pleasure to please her lover, the speaker.