How can iMessage send from my old phone number that doesn't have service anymore? So my little brother used iMessage through my mom's iPad. He was just being funny and sending pics and cute little memes. 

However, in the process, he sent my mom a few messages from the iPad. However, they popped up from my phone number on her iPhone. What I mean is that it appeared as if I had sent her the message. 

I looked into and the internet said that it was because my iCloud account was synced to the iPad. However, I have never even used her iPad and it has also a different account. 

The weird thing is that my phone hasn't had service in a month. And now I am freaking out and thinking my little brother is a computer whiz or a secret hacker. 

Please help because I am so confused. Thank you to those who answer and provide clarity on this situation.
I think there is only a solution for this and is the one that you have found on internet. 

More precisely, no matter if you are not using you iPhone or even your number configurate to iMessage in your phone, if you mom's phone marks the message from iPad under your name this mean only one thing and the thing is that the iMessage account on your iPad is configure with the same iCloud account (email) that you have on the iMessage of your iPhone.

You can always change this settings. The interesting thing's for you is to figure out who did this ;-)