Na, you wont have to cut them.Usually people with long hair use a technique called backcombing.But also you could get a dred perm (thats if youre willing to spit out alot of cash).The results are great and it works instantly.
I have locs myself. Its not exactly a high maintenece, but you still have to take care of your hair. I was daring and started my locks on my own, and its been going very good since then. If you do decide to do it, make sure you go to a place that doesn't use beezwax. Some may say its ok to use it but it can cause build up and your hair may not have that good shine. I used beezwax and my hair looked dull. I went to a shop and they washed it out and and started me on loc butter. I use that now. Since I have dry scalp, I tend to wash my hair every 2 weeks. If you don't want to have locs, and you are far in the process, you will have to cut them, BUT you can always let it grow out and not twist the new growth and cut it at the part that is still locked. You will have short hair, but not bald.
and pro....tell you brother to check out henna...its a natural dye, but depending on how dark his hair is, he may have to do it a couple times before it really shows.