It is not possible to share or transfer content between accounts on Google Play, even if you own both accounts. If you have multiple accounts on your device, make sure you’re signed in to the account you want to use before you complete your purchase.
If you’ve bought an app on the wrong account contact the app developer. They may be able to refund your purchase so you can buy it again on the account you wanted to use.
Note: You can share apps and digital content with your family if you use Google Play Family Library.