10 year old step son

Does anyone have a 10 year old son or close to that age where he doesn’t take showers for days. Maybe longer? We only get him every Tuesday and every other weekend. The rest of the time he is usually at his moms or his nanas house (her moms) we try to get him more but she won’t let us. That’s besides the point and a whole other story.. We picked him up today. Hadn’t had him since Tuesday. He took a shower here. His hair is a greasy mess today, and he has a small body odor stench, we asked him when the last time he took a shower and he said at our house Tuesday. Before he has gone an entire week without showering. So like if he stays with us Tuesday and we don’t get him until the next Tuesday. He usually hasn’t showered. We asked him why he doesn’t just take a shower himself and he shrugged his shoulders. His mama nor his nana tell him to take a shower we know this because he told us.. Only we do and we try explaining to him that he is getting to the age where he needs to shower every day or at least every other day and he’s getting to the age where he shouldn’t have to be told. He just looks at us. He doesn’t brush his teeth unless he’s told either. He’s gone a week + without brushing his teeth. And usually only does it when he’s here. Just like showering. I have two brothers and I don’t remember them being like that. Idk. Is this normal behavior for a 10 year olds? Just looking for some advice or suggestions. No hate please.

EDITED: Staying anonymous for a few reasons. But my fiancé has tried talking to his sons mom and nana. They say they do tell him, and then they say they shouldn’t have to tell him. Honestly, they just don’t pay attention enough or care enough to even bother with it. They put him in front of a screen and he sits there from sun up to sun down. No joke.

My fiancé and I have tried talking to him together, and separately. We just don’t know what else to do.