In determining whether the valid consent of any person whose consent is required is withheld contrary to the best interests of the child, or is unobtainable, the circuit court or juvenile and domestic relations district court, as the case may be, shall consider whether granting the petition pending before it would be in the best interest of the child. The circuit court or juvenile and domestic relations district court, as the case may be, shall consider all relevant factors, including the birth parent(s)’ efforts to obtain or maintain legal and physical custody of the child; whether the birth parent(s) are currently willing and able to assume full custody of the child; whether the birth parent(s)’ efforts to assert parental rights were thwarted by other people; the birth parent(s)’ ability to care for the child; the age of the child; the quality of any previous relationship between the birth parent(s) and the child and between the birth parent(s) and any other minor children; the duration and suitability of the child’s present custodial environment; and the effect of a change of physical custody on the child.