It was within the juvenile court’s discretion to request an offer of proof as a condition precedent to a contested hearing on whether the sibling exception to adoption applied. Therefore, at a section 366.26 hearing, where the adoptive parent testified that she had intended to adopt all four minors, but that legal guardianship was better for two of them because they would receive additional educational benefits, the parents’ offer of proof was insufficient, and the hearing was properly denied. Due process is a flexible concept, and a court can require an offer of proof to clearly identify the issues so it can determine whether it is sufficient to warrant a hearing.