Mine is and always has been.
Family' friends and relatives that we saw regularly, but not every week, always commented on how I was quiet and shy - I wasn't, my sister was always that gobby that nobody else got a look in.
She is nearly 50 and I am 47, still hasn't changed now - always thinks she knows best. Will screech at me across a room to get me to go to her if we are out - think Bianca's "Riiicckkkkyyyy".
Used to drive me nuts when I was growing up, we were quite distant in our 20's but are very close again now.
I cope by ignoring her or telling her to shut up. I am brilliant at literally switching off to any conversation she can have and she won't even notice that she is the only one talking 
.
She knows that she is like this because I tell her, so do my nieces and my Dad, her husband will tell her to give it a rest sometimes if we are all eyerolling at her and he comes in.
I also cope because whilst she is literally a pain in my arse she would also be my fiercest defender (which has been annoying in the past because I can actually stick up for myself) and would be there in a instant if I need her. I know it comes from a place of love.