a. You have five people to talk to. Unlike you, I don't have someone to talk to.
b. You have five people to talk to. Unlike you, I don't have anyone to talk to.
a. You have five people to talk to. Unlike you, I don't have someone to talk to.
b. You have five people to talk to. Unlike you, I don't have anyone to talk to.
Are both of the above grammatical?
English is a funny language. The first one contrasts with "Like you, I do have someone to talk to." I advise you to use the second one only if you omit "Unlike you".