Just to give another perspective - but I wonder whether you are projecting your ideal of what a wedding is about onto their wedding, and maybe your ideal of a wedding is not shared?
This always seems to come up in weddings thread. Some people seem to think that weddings are about the uniting of two families (as is referred to in Christian marriage ceremony), but others see this as an outdated notion, and see weddings merely as a contract between two people (as is the focus in the modern secular marriage ceremonies). I think both views have validity, and neither one view can claim to be 'correct', but I see that they cause problems when different people hold different views.
I personally, see weddings as being about the couple - not about the joining of two families. Therefore, I wouldn't think to necessarily include all of mine or my husband's family in the events. Neither would I expect to be included, or be hurt by not being included in the wedding ceremony when my brother gets married. I'd see it as a lovely gesture, but would not think that I should have any involvement simply because they are family. To me, this would be expecting too much. But obviously, you hold a different view of marriage - and that is fine too.
I hope explaining a different view of marriage helps you to see that it is not a slight or rejection of you, and I hope that helps you not to feel hurt, because I really do not think it is as such. It did not occur to me to think you must involve family, just because they are family.