Last October I went to the hospital with pretty horrid pains in my upper chest. Felt like my ribs were made of barbed wire. A CT scan (you really gotta try it, it's freaking rad - you become the Human Torch for fifteen seconds) revealed it was a blood clot in my lungs, courtesy of another treatment I had going involving prolonged steroid use.
Anyway, they put me on blood thinners for a while, and I suspect your brother will get the same treatment. Initially, they need to get it working in you quickly, so I got to self-inject one subcutaneous syringe a day for about a week. Basically you grab your belly fat (if you're really fit, you'll have to do the upper thigh - nurses won't let you Rambo-style it) and inject there. Then they start the pills: Warfarin/Coumatin is what you take daily. The drug is cheap and the side effects (you bruise easily) are very minimal, according to the pharmacist, just don't go and get in a situation where you're going to bleed heavily, for obvious reasons. Every so often you'll go for an INR test, where they test how thin your blood is and adjust your blood thinner dose accordingly. Depending on your condition, you'll want a different reading. If it's too high, they'll give you vitamin K to thicken your blood, which for me came in the form of vitamin K-spiked orange juice. It's important to take the pills at the same time every day, especially before the INR test day or it'll skew the results a bit.
Was on Warfarin and Coumadin for about six months before the doctor told me it was probably all good. They ran an ultrasound of my legs just in case (the reactions you get walking into a waiting room of pregnant women as a 21-year-old male are also rad, especially when you wink at one and say "it's a girl~") and greenlit me to stop the meds.
That's pretty much it. I hope your brother recovers!
edit: i spell sometimes