Numbers calling all iPhones in family household?

My family and I all have iphone 5s'. We share the same Apple ID because we're under the same plan, but we unchecked each other's phone numbers in settings so that we wouldn't receive texts from other family member's contacts. Recently, two numbers called my mom's iphone, but as her phone was ringing, all of ours began to ring, too, the same number calling. She tried calling her iPhone with a different phone, and the same result arose. What is the issue and how can we fix this?

I'm having the same problem since I installed iOS 8 on both phones. I also need this answer.