As much as it sounds like its my brother, I really don't think so (unless I am lying to cover for him). Of course I checked his phone and games as soon that I found the transactions came from there and there really isn't any evidence of purchases inside the games. He doesn't really protect his phone from his family since I know his password and he sometimes asks me to use it for him to level up characters, so I would have noticed any irregular increases in the currency or characters.
My original theory was that someone used something to spoof purchases from google as app transactions using the information that my mom plays those games under my brothers e-mail. When we both checked his E-mail, apparently the E-mail was named after my mom as the owner and had wrong but close city information. I have also noticed there are some people with same issue within the previous months via google. Can someone tell if spoofing transactions is actually possible.