IPhone sending messages to other people?

So for the past few days, whenever I text my parents, like if I text my Mom my dad will get it or if I text my dad my mom will get it. When I try sending a message to either, I'll get the ones my mom and I were on but it'll have a different number on top. I checked iCloud and not any of us are sharing the same address, we just share the same account. I hard restarted my phone thinking it would help but it didn't. My phone made a static noise twice, I'm also being told by my iPhone that the battery has been degraded. I'm not sure /what/ to do. I'm absolutely sure my phone is slowly dying though.

"we just share the same account". You answered your own question. ICloud is not designed to have a single shared account for multiple people. Set up your own iCloud account.