My brother is in Iraq until September which he will be returning home for a 4 week leave. I start my hormones this Thursday and that's approximately 5-6 months away from when he will be here. I was wondering how much I would change in that amount of time. I keep asking myself will I look different or relatively the same? So my question to you is how drastic was your changes between 5-6 months. ( I know everyone transition is different) I'm just trying to get an idea, some real life examples .

He'll know...no doubt about it

Breast develop at three months
Skin starts to soften immediately
Muscle mass drastically reduces you to
The strength of a 120 lb girl...
Emotions become stronger
Waist. Narrows and butt grows....

By month 6 it's possible to be gendered as a girl
Especially by strangers

Different people get different mileage from HRT ( YMMV ). There are numerous factors that can help influence ( such as age, health etc ) as well as what kind of HRT regiment. Ultimately, you won't know ahead of time. There are ( sadly ) women here who have had minimal effects after years. And there are also some women who develop in a considerably shorter time frame.

I'm personally just over a month into HRT. Physically, there are some minor skin changes, some muscle loss, and the beginnings of breast growth ( AAA cup ).

So, see how you go once you start. Maybe you'll be one of the lucky few who develop quickly. 

Probably he'll see it.

Ive been on a few months ago.

My friend who I hadn't seen in awhile barely recognized me.

I agree with others . Even if your changes are slow it'sikely he will notice something about you is a little different . He just may not know what or say anything about it

Around 6 months is when the changes really start to become noticeable. He will definetely notice, especially if he hasn't seen you for a while.

I asked some of my co workers yesterday if they noticed much of a difference and they said for the most part not really. Then I showed them a photo of me pre hormones (8 months ago) and they're like "who's that?" and "did you look like that when you worked here?" Uh ya ive been working there for almost 3 years.

By 6 months, I was a D-cup and had changed so much that friends didn't recognize me, and went to a baseball game in a loose jersey and jeans and combat boots with a baseball cap on and still got gendered female. So like everyone says, your mileage may vary, but for me I was definitely ready to go full-time (as in, getting weird looks or "misread" as female if I went out in boy mode and pretended to be male) at around the 3-month mark. I actually was kind of unhappy with that, since I wasn't ready mentally yet...