I have to admit that I would be annoyed. More so if it was my sister who chose the same date rather than if it was my brother, and that is, without a doubt, due to petty sibling rivalry and personal insecurities!
In either case (were it my brother or my sister), what would annoy me the most was the lack of ability to really celebrate my wedding anniversary with my husband. Since we were living 800km away from where we got married (and most of our family and friends), we chose to get married on Thanksgiving weekend (Oct 8th, 2005). It worked out perfectly, pretty much everyone who was invited came, we had a wonderful weekend…
BUT…
As is tradition, Thanksgiving weekend is spent with family. So for the past two years, hubby and I haven’t been able to celebrate together on that weekend. It’s petty, because there are other weekends to celebrate together, and the date doesn’t always fall on the long weekend, but that’s the way it has been so far.
So if my sister also had an anniversary on that date… well, knowing her, it would be a semi-public thing every year (well, public within our family, with constant reminders of the date, congratulations expected etc., that’s just the way she is!) So it would bother me to lose a little more of “my” special day. My brother… well, I know he wouldn’t make a big deal out of it, so I’d be ok with it, but who knows who hypothetical-SO would be and what she’d act like!
I kind of feel the same about my birthday; it’s only a week away from my husband’s birthday (same year, one week apart), and since we already end up pretty much sharing, I wouldn’t want to share that day with my sister or brother too!
Totally selfish, totally irrational, but that’s just how I am. I would get over it, though, for sure. It would be something I’d rant about to my husband, and mull over personally for a bit, and then move on. I don’t own the day. I don’t know about my brother, but I know my sister would much prefer a spring/summer wedding anyways, so it’s unlikely to be an issue!