what a georgous little angel you have.
That is so horrid what your ex-friend done, that is unforgivable.
With regards to telling other sibilings. I lost gillian 3 weeks ago and my 3 year old knew that she was getting a baby sister. she does understand that she isnt here any more, and still talks about her, she says she is a star in the sky.
You will know the right time to tell your boy about his brother, dont feel you need to do it to soon, just when you are ready. As he grows he will understand more and more and im sure his big brother is watching over him all the time.
sending you love and hugs, thanks for sharing your pics with us all.
xxxx