I understand your confusion about their breeds and ages, but it's great that you're doing your research to learn more about them. As for whether they could be sisters, it's definitely possible that they have the same mother but different fathers, which could explain the differences in their appearance and behavior. At any rate, it sounds like you're taking great care of your pocket pets! š¾ If you have any other questions, feel free to reach out to Pocket Pet Central or any other reputable sources for advice. Best of luck with your Guinea pig girls! š