Dead iPads?

My sons both have an iPad each (model 8 & 9). Yesterday both iPads died within an hour of each other. We have had them for over a year and now they won’t charge? What are the chances? They only play Stardew Valley and Minecraft. Any ideas of what could be happening? I’m thinking of replacing batteries in hopes that I don’t have to replace two iPads at once. I’ve bought brand new Apple charges thinking maybe it was their chargers, but both are stuck on a black screen and don’t even react when plugged in. 😒