人間 (ningen: human being)
友人間に (yūjinkan ni: among one’s friends)
Did you notice what happened? With the mere addition of 友, the yomi changed from ningen to jinkan. In some ways, this isn’t such a big shift; NIN and JIN are similar-sounding on-yomi of 人, just as KEN and KAN are similar-sounding on-yomi of 間. But with voicing, KEN turned into GEN in ningen. All these small changes add up to one big difference when it comes to ningen versus jinkan.