When my husband sends me an iMessage from his iPhone 5c it sends it to him. If I send him a message from my iPhone 5c it send it to me. This has just happened since we updated yesterday.
You are using the same Apple ID or the same cellphone number to receive iMessages on both iPhones' iMessage clients. Doing so will lead to you receiving your own sent message, like I am:
Here's a quick fix:
- Open Settings>Messages.
- Tap "Send & Receive".
Tap "Add another Email".
Type a diiferent email ID. It will now show a "Verifying..." status. Open that e-mail inbox and confirm verification.