Tell your "D"Sis and "D"H to STFU, what do they hope to achieve from trying to scare you??
My first was 9lbs 5oz and I'm so glad I didn't know in advance as I'd have worried and actually it was fine. For context, I'm 5'2" and a size 8-10
. He had a bloody big head, which meant I had pain in my symphisis pubis during pushing his head out which was fucking painful, but I think he wasn't in the best position, and the actual labour was fine. I had a home water birth with g&a, some tearing (but I didn't feel it happen, didn't care while being stitched as was on such a high, and it healed fine). Wouldn't have torn if he hadn't decided to do a little dance when his shoulders were just out and I was waiting for the next contraction to help with the rest of him. He's still impatient now. :)
My second was a little early, and still 7lbs 12oz. Similar labour (quicker, though), didn't bother with g&a but that was more knowing what I was doing I think, and still tore me (I rushed things, silly me).
Stay upright, stay calm, don't bother pushing consciously until crowning, and you've got the best chance of these things working out as easy as possible.