To be truthful is it plausible some people are clueless to what their true identity is?

Some of the things said of identity are:

1. The state or fact of remaining the same one or ones, as under varying aspects or conditions.
2. The condition of being oneself or itself, and not another.
3. Condition or character as to who a person or what a thing is.
4. The state or fact of being the same one as described.
5. The sense of self, providing sameness and continuity in personality over time and sometimes disturbed in mental illnesses, as schizophrenia.

Some people by their behavior appear to not know who they are. Some people say they are X, and will defend it tooth and nail while they act like Y, or something else. If a person says they are this and that, but act nothing like what they claim, is it plausible they are clueless to whom they actually are?