Hmm I'm confused by the usage of "in that" here too. This sentence, "It will nevertheless resemble us in that it should communicate with its fellows.", I think could be deciphered to mean something like this: "It will nevertheless resemble us because it should communicate between its fellow species like us humans do. " I'm not sure if I am correct.. but I don't know what else it could mean. Ending the sentence with "fellows" is odd english to me. Hmm unless "fellows" is a specific term that has been defined by a previous sentence you're reading.

As they say "in that" is a connecting phrase. It means similar to "in the following way", "in the way that will now be explained". "& I say this because ...." . "fellow countrymen" does not mean friends, only others of the same country/type.

It is just functioning as a sort of connecting phrase, to connect the "resemble us" with a phrase showing the specific way in which it will resemble humans. I'm not sure of the specific grammatical term for this!