When my brother and I were born, we were twins, and we absorbed all my mother nutrients, which she said made her very sick. She couldn't even drink water, that's how sick she was. We were born two months before our due date. I was 4 lbs and and he was 3 lbs. We had to stay in the hospital for a couple of weeks because we were preemies. The way things were going, with my mom being sick and being prematurely born, it affected our growth. We are now 16 and 5'2" and 5'3". Our dad is 6'1" and our mom is 5'3". We have a small amount of under arm hair, we have a few strands of chin hair, and we have arm and leg hair which you can see up close. We are a size 5 in kid's clothing. We are ripped for our size, but we look like we are 14 yrs old. We weigh about 104-110 lbs. We still haven't experienced our growth spurt yet because I haven't seen any rapid growth. We have pubic hair, but it doesn't lead up to our thighs and we don't have a happy trial. I was wondering when will we finally hit our growth spurt and start looking like our actual age. My brother had a lump under both nipples in 8th grade and his went away. Mine came at the end of 8th grade and I still have it today, and I'm a sophomore in high school. I was wonder why is mine taking longer than his and I'm older than he is.
Since you are twins, technically you are the same age. You came out of the womb first, but you both were conceived at the same time. I suppose that you are fraternal twins, meaning that you come from two different eggs; instead of being one egg that split early on. That would account for your slight differences in growth, though even identical twins don't grow precisely the same.
It isn't unusual for multiple birth children to be born premature. Yours was an unusually early birth for twins, but it wasn't due to the fact that you were twins.
Premature children do tend to develop later than children born near their due date. Premature children also tend to be smaller than their peers.
It sounds like you are in stage 3, but I can't say how far. I have to guess from your description because I can't see you. My guess is that you are right at the start of your growth spurt, but it is possible that you won't see a huge increase in size all at once. Some boys grow faster, but it is spread out more. A growth spurt is typically defined as growing more than two inches per year. I would not be surprised if your brother grows faster first and you will catch up a bit later.
By the time you reach your adult size, you should be at a minimum be 5'8" (the average of your parent's heights). You may be taller than that, but that isn't something I can easily predict.