Dog help

I have no idea where else to post this but my youngest dog (will be 2 y.o. In July) randomly peed on my side of the bed nowhere near my husbands. I took off the sheets and what not today because I was gonna clean them. I just came back to put them on and there was a huge piss spot. I did take them out not that long before I'm assuming he peed there. I just don't get why all of the sudden he peed on my bed. If anyone has an insight please let me know.