(b) For the purposes of this section "extended disruption of custody" shall include, but not be limited to, a prolonged separation of the respondent parent and the child for at least twenty-four continuous months during which the parent voluntarily relinquished care and control of the child and the child resided in the household of the petitioner grandparent or grandparents, provided, however, that the court may find that extraordinary circumstances exist should the prolonged separation have lasted for less than twenty-four months.
(c) Nothing in this section shall limit the ability of parties to enter into consensual custody agreements absent the existence of extraordinary circumstances.