Kohlberg's Moral Stages
Level 1. Preconventional/Premoral (egocentrical, responsive to rules and see reinforcements as positive or negative)
Level 2. Conventional/Role Conformity (want to please and help others and care about others expectations)
Level 3. Postconventional/Self-Accepted Moral Principles (understand right and wrong, considers the law and institutaional rules when making decisions)
Mr. Van Daan and Otto Frank are on two different sides of the Kohlberg spectrum. It's difficult to determine their real character, because they were put in such an extreme situation. The following information is my interpretation of two characters moral levels of development.
On one side you have Otto Frank who willingly allowed others to come into hiding with his family. He constantly gives of his time, resources, and knowledge to help others, without wanting anything in return. Considering his circumstances he didn't follow the law and instead went into hiding, so he didn't meet level 3. Under normal circumstances, considering Otto's character I believe he would fall into level 3.
Then you have Mr. Van Daan. He steals food, without considering other people's feelings. He also didn't want Mr. Dussel to move into the attic, because it would mean less food for him. He also puts down Anne and tells her to be more quiet, like her sister. This is very egocentrical. Almost all of his behavior consistently lands him in Kohlberg's Level 1 Stage.