How old are these kittens?
If this is an older kitten- 6 months or better, he might either be playing, or stressed. Is the litter seperated for some reason? Is there a good place where this kitten can hide? Do you have a cat carrier available? If so, wash it out really well and dry it off, put in one old bathtowel for a bed- feral kittens are not used to "soft" things. Drape a cloth over the carrier leaving enough room for the kitten to get inside, prop open the door and leave this "kitty cave" in a dark corner of the room so he can hide.
Do not force the other kitten out of hiding, instead, go into the room and sit down on the floor near the bed. Take out a book and read softly to the kitten out loud. Keep your tone low, he will hear you. When you leave, leave the kitty a tasty meaty treat where the imprint of your body was on the floor. Do this on a schedule so the kitten will come to expect your visits at certain times during the day.
Also feed, water and scoop litter pans on schedule as well. He is hiding because he has no concept of humans. His safe place is under the bed, getting on your hands and knees and pulling him out to force him to accept you, will only set you back in the bonding process. Do not put the food and litter pan under the bed, but rather near the bed and always in the same place. Do not have the food saucers and litter pans so close that the litter can contaminate the food area. If this kitten does come out of hiding, avoid looking directly at him. If you make eye contact, blink your eyes several times slowly then lower your head. Try not to make eye contact for this will just serve to scare the kitten more.