Hello my friend. If your daughter does not want any more contact with her dad right now, then cease contact. When she starts regular school in Kindergarten and the issues of families and Father's Day comes up, then she may want to begin the relationship again. It will be perfectly fine to wait a while...until Kindergarten The great thing is that she knows about her dad and has met him...so that it is not a big dark secret.
With regards XXXXX XXXXX half brother, she is still rather young to understand the complexities of having a half brother that she will not have contact with. She will want to see him and have a relationship with him. With that issue, you can wait a little longer to let her know about that issue...maybe until 2nd grade when she can grasp and process the information a little better.