It can be very dysregulating to have a parent come into your life that has been absent and I certainly understand your ambivalence. But I would look at your motivation in the decision-making process. To quote Buddha: “Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one who gets burned.”
Your wanting to punish your father, a man who has not cared what you did or felt or accomplished for 27 years, is leaving you with the hot coal, not him. You do not have to make your brother’s nor father’s quest yours, but you have to allow the choice to be one that genuinely suits your needs. Otherwise it puts you in orbit around theirs.
You did not mention your brother’s age relative to yours, but this may be partly why he is in a different place wanting the connection. He is tracking down the same-sex parent and I would hope he comes to understand that his needs, by both age and gender, may be very different than yours. You and your brother may also want to employ the skills of a family therapist who has some expertise in reuniting families. Here is a list of therapists you can review.
You obviously have done well taking good care of yourself, and I suspect that trend will continue. Keep your needs and timeline for meeting them as a priority. If you choose to meet him only do it when you are ready, not pressured. Otherwise your resentment may undo whatever good might come from the meeting. Good things can come from such a meeting, but only when your willingness and readiness are combined.
Wishing you patience and peace,