Guinea pigs are socialble animals and will most likely get along with each other.
It's normal for a guinea pig to be afraid of you at first, and some guinea pigs, depending on personality, are always a little shy. However, with patience and love, you can almost always make good friends with a guinea pig. The younger they are when you start, the easier it will be to gain their trust.
The thing to remember is that you are very large and frightening to a guinea pig. Also, being picked up is _very_ scary, since guinea pigs aren't really climbing or jumping sorts of animals the way, for instance, hamsters are---they're used to having four feet solidly on the ground. It's much easier if you start when they're little, so that your hand can support more of the body at once. The best way to pick one up is to place one hand under the belly and lift, then as soon as they are off the ground, place another hand under the hind legs so he (or she) feels secure and supported.
Put him in your lap---maybe on a towel so you don't have to worry about "accidents"---and pet him to your heart's content. Some guinea pigs also like being held standing against the chest, with the nose pointing up towards your face, or cradled in your arms at chest level. Try different positions, and you should be able to tell which one(s) your guinea pig likes by how restless they are. This is a good time to give fresh vegetable treats, so he feels positively about the experience! As soon as he begins to squeak or become restless, let him down. Besides the fact that he'll become enthusiastic faster if he isn't imprisoned on your lap, it also may be a sign that he's about to pee.
Some guinea pigs never feel comfortable being picked up, especially if they aren't handled a lot when they're little. This doesn't mean that you can't have a good relationship with your pet, though, just that you have to relate to him (or her) where he's more comfortable, namely on the ground. The best time to do this is during play time, when he's let out to run around the room (this should happen every day, so they get enough exercise). Lie down on the floor, so you aren't so tall and frightening, and offer a piece of vegetable to your guinea pig. While he's eating it, reach forward slowly to pet him. If he runs away, let him finish his vegetable and try again later. It may take patience, but eventually the shyest of guinea pigs should sit still for you to pet him, and even come over to be petted. The more time you spend on the floor with him, the faster he'll get used to you. Also, the less you chase him around to pick him up the less afraid of you he'll be, so if your guinea pig lives in a cage, try to set up some sort of ramp so that they can get back into their cage on their own. If you put fresh vegetables in there, or just rattle around their pellets a little, I guarantee they'll go back into their cage without more forceful urging.
Remember, the more time you spend with your guinea pigs, the faster they'll become friendly with you!