DD has always been a dinky dot. She was 7lb 10oz at birth but looked much smaller - the surgeon at the birth (CS) actually asked that she be weighed again as she didn't believe she could be over 7lb in size, she thought she could only be around 6lb based on her size. DS1, her older brother, had been huge in comparison (over 9lb born) and I was expecting her to be big too so I'd only brought size 0-3 month sleepsuits to hospital. They were massive on her! The arms and legs on them were empty because her entire self fit into just the body part of the suit. I had to send DH out for first size things.
From then on she grew, but slooooooooowly. By six weeks old she was on 2nd centile and has hovered between there and the 9th centile ever since. She stayed in first size until she was around three months, then she went into 0-3, at a year old she was wearing 6-9 months.
Now she's 4yo, she weighs 29lb, wears size 2-3 school uniform (it is an absolute bugger trying to find small uniform sizes in the right colours!), and has size 7E feet. She's looking a little bit full around the face at the minute so I'm hoping she's about to have a growth spurt. DS2, 22mo, is catching up to her. He's 25lbs so it probably won't be long until he overtakes her.
I get comments now and again. At Halloween we took her around near my parents' house and one of their neighbours shouted me back to say that "the baby" had taken a pack of Love Hearts and would she be able to manage them? I also get people tell me what a good talker she is or how good she is at x, y, or z "for her age". People presume she's younger than she is. There's a carvery near us that feeds children aged two and under for free if they're with paying adults, they get a little dish for you to take to the carvery. Everytime we're there, they bring her a dish and every time she gets offended because "I is NOT a baby!" and I think to myself, "hush child, you're about to get a free lunch..."
Last year the HV got us to keep a food diary to check that she was getting enough calories and agreed that she was, they concluded she's just small made. She doesn't eat huge portions, some days it seems like she lives on fresh air, so I use full fat milk, butter, cheese, avocado, etc to boost her calorie intake a bit.
I think ultimately, someone has to be the smallest, so it may as well be her.