As I said above, my sibling is transgender, so here's a few points based on my experience.

1) The only difficulty I had was with pronouns. When you've been using 'he' for decades its is damnably easy to say that instead of 'she'. It is worth getting an understanding that this is stupidity on my part, not a statement of a viewpoint.

2) It is especially difficult when discussing the past. I tend to use 'he' for before the operation and 'she' after, but that does depend on the exact situation.

3) His/Her concern was very much about how people would react. This meant the whole thing took decades, including times afterwards when she dressed as male. No-one should underestimate what has to be gone through while finding your way.

4) Everyone *I* know who has been told had precisely one reaction - sorrow for the pain he/she went through without letting anyone know.

5) I am sure there are some she knows who didn't have that attitude.

6) And there is one person who not a close relative of hers who I would not tell, because I think that relative would react badly. It may be mistaken on my part, but I am not raising the matter with them.