From a young man in the U.S.: Is convincing a child that every man her mother is with is her father considered mental abuse also the original father is alienated from childIs This Child Abuse?
It may be. I don’t have enough information. It does suggest that the mother wants to maintain the fantasy of an original family despite the facts. Usually this stems from religious or traditional beliefs that make it difficult to accept that life hasn’t gone according to those rules.
If you are asking about yourself: You are 27. You don’t need to continue to be alienated from your father. Contact him and find out for yourself what kind of person he is. If you are dating someone who is doing this, proceed with caution. For the benefit of the child, don’t participate in the fantasy. The child is probably confused enough by a history of changing “fathers”. You don’t want to add to that confusion and the distress it is sure to cause.
I wish you well.