You can try to change one of your WhatsApp's verified number to the another number. But I don't know if it really works, since the another number already has been bound to a WhatsApp account.
Are you using two accounts on different mobile phones? Then another method for you is using tool to transfer WhatsApp chat history from account A(phone A) to the account B(phone B), and then delete the account A, for your personal info safety, by going to WhatsApp Settings > Account > Delete my account.
After that, all your WhatsApp messages and media will be stored in your account B on phone B. No need to worry about group chats, they will be moved together.
But sometimes a bug of WhatsApp will happen. That is, when you login WhatsApp on a new device, you will automatically left the group. So then you will have to ask to join the group again on the new device. It's happened to me a few times. I don't know whether it will happen to you, I hope not, just to remind.
— modified on Aug 11, 2017 4:29:41 AM