You are going to need separate corrals for each. Get the stallion gelded soon as possible. I know you know that, but if I don't say it I would feel I did you a disservice. Ok, once in separate corrals, get in there with a rope. Have your halters ready. Each one will take a while. The colt at 5 months is old enough to wean, so this is weaning time. But as I said, get your rope handy. Question, have you ever roped anything before? If yes, proceed. If no, go practice. you're going to need to get a rope on them and play with them. There is a LOT you can do with just a rope before you even try to put a halter on one. Once roped, give a tug and see if they will look at you. If yes, go from there and ask for more. If no, it's more work. Get them to look at you, then ask for one step. That's it, just one step. If you get that step, back off and let them think about it. If they are still looking at you with an easy eye, ask for another. It all starts from that one step. I have done a lot of unhandled horses of a lot of different ages. You can leave your rope on one in a corral. The lariat will loosen and slip off. Or, if the horse has progressed enough that you can handle it, you can remove it. But if you leave it on, that horse stays in that corral. There are a lot of lessons a rope can teach a horse all by itself, valuable lessons. Now before anyone reading this gets bent, I have done this and never had one hurt themselves. One lesson I particularly like is they learn if they step on their rope or lead rope, All this is done IN the corral, they learn not to freak out, they learn to simply step off it. Saves on reins later in life. I always left lead ropes on my foals until they were easy to walk up to. I have left lead ropes on older horses I halter broke as well. In the corral, they are not going to get it hung up on something and they learn to give to the rope. Makes things later on a lot easier. Once you can walk up to one, rub it's forehead. Don't go for all over yet, they're not ready. This has to be on their schedule, not yours. Walk up, hand over hand on the rope, and merely rub the forehead. Then step back. Ask for that first step again. If you get it, rub their forehead. If not, ask again. If they break, and run from you, they're not ready. Work them around the corral, and then ask again. It all starts from there. But that's enough to get you going on them. Good luck to you! Let us know how it's going. I know others use a different way, and that's fine. The more different ways that are presented will give you a choice. But this is how I do it. it works.