I geuss it's a tiny bit off track but in the past when people birthed at home surely thier older children would have been present. I was born at home and my older sister was present and helped give me my first bath and so on. At my birth the midwife told her that she was going to have to look out for me and to this day she still tries to.
If I were to have another baby I would want my younger ones there with a carer who could remove them if needed. I would proably figure out a pre-arranged code phrase to say get them out of here in case I needed them gone for any reason.
I geuss our attitude is going to be coloured by our perceptions of birth. If we see it as bad pain and scary then we will pass that attitude on to our children but if our children know that it is good pain and aren't scared of it then it becomes a differant situation.
It's just one of those areas where all families have to find thier own solution.

ETA - I tracked down *Yvette*'s birth story with her twins. She had both her oldre children present. It's here. She also had her oldest at Angus's birth.