Interesting - while these tend to be vague so they can fit the general range in the population it blows my mind how much I am like an only child/first born. Good thing there were eventually siblings for me, according to this I could have been even less pleasant had that not happened.
I don't think this has to pertain to someone you love romantically. It could, but it doesn't have to. There are just people that you can be more of yourself with than anyone else, and once you leave their presence, it's like you have to hide behind your mask again. So you would just rather stay with them and not leave...or at least, that's how I feel.