Fleur you are going to be a fantastic Mother! This is one of the very few qualities that nature blessed us with no matter what.
Do not let any one be the judge of that. I would ignore them and let them sip some kool aid for a while.
Some people just do not know how to be happy for others, it's always something. If they are good friends of yours and you value their friendship I will call them out on it, and be open about how their actions not them made you feel. Otherwise ignore.
want for your sister I totally recommend speaking to her do not ignore. Respond to her email. My DP was a bit like that with his siblings and it frustrated me that no one ever thought to correct him.
I was upfront and said he was jealous, to which he did not defend perhaps shocked that I was able to source it. Anyway since that conversation I have seen a big change in him, because I helped him confront his issues and deal with it.
We all have it, and need to make a conscious effort to manage it. Such is life. Good luck.