Yes, that's very much a boy! Compare the other kittens to him, if any look different that one is a girl. They'll need to be neutered soon, be especially careful if one is a girl, because females can get pregnant as early as 4 months.
They all look like boys to me. You'll need to get them neutered soon. Cats reach sexual maturity at around 5-6 months old and with three boys in the house they might start spraying to assert dominance. Once they've started spraying it's difficult to get them to stop, so better if you get them fixed before they start.
Your boys are big enough to be fixed now. Do you need help finding a spay and neuter clinic near you?
Thanks. I am in touch with someone who will be helping me getting them neutered. Already got the mother spayed. These are 4 months old. One of them is spraying already, i think. They are all semi ferals and i have no experience in taming but trying. One has become quite friendly though. I just hope they all get tamed and find a kind forever home.