If a probation officer determines to recommend to the court that a minor alleged to come within Section 300, 601, or 602, or adjudged to come within Section 300, 601, or 602 should be removed from the physical custody of his parent or guardian, the probation officer shall give primary consideration to recommending to the court that the minor be placed with a relative of the minor, if such placement is in the best interests of the minor and will be conducive to reunification of the family.