I have a brother. I often wish I had a sister, or just more siblings in general. I think it would be a lot of fun to have a lot of siblings, though I don't think overpopulation is a good thing.

It's normal, but it's something that you should try to change. It's easy to become anxious and think about all the things that could go wrong / think that people won't like you if you go out, but ...

As long as it's not very hot coffee (unless you have a high quality straw that is not going to melt / leech plastic into your drink). Warm coffee is fine. I think it's normal to want not to stain...