I’ll answer my own Q. When my MIL asked me I told her no. I don’t remember ever once wishing I had a brother. It never occurred to me once that he might be, or should be, a protector. I hear that a lot when I ask people this question. Do brothers really do that? I never thought in terms of needing a protector, my parents kept me safe in my mind, and overall I felt safe anyway as a child. I just never gave having a brother a thought. Is your brother going to be around the very minute you need protection? Protected from what?
I know my sister once said she wished we had more sisters, we were in our early teens, I thought that was nice, and I agreed at the time, although I hadn’t thought about it previous to her saying it.
My observation is big brothers do some mean things to their younger siblings girls and boys, including physically pushing them around. Maybe some boys don’t do that. I don’t understand idealizing having an older brother at all, but I have no experience with it in terms of day to day.