Activation Lock

Does Apple remove iCloud lock? I am stuck with this "Activation lock" on my iPhone 6.

Long story short, I am the original owner of the iPhone 6, gave it to my brother a few years ago. Now I gave him a new phone and took the iPhone 6 back. However my brother has forgotten his apple id and pw so now I can't unlock/activate the phone.

I still have the Apple Invoice I received when I purchased the iPhone 6 including the Loan agreement back in 2015.

Many thanks for all the advice and answers.