My brother, I'll call him M, took his own life in April, 2018. M had been terribly depressed and had not been well for a while, but despite all that my younger brother, J, his wife, S, and I did we could to help him. M had lived with J & S for 20 years on a ranch in Oklahoma and passed away there.
Four months after M's death and a week before his memorial service in Texas, where he grew up, I got a call from J. When I picked up there was nobody there and the line was dead. I looked at missed calls and saw the call from J and another from a number that looked very familiar, but I could not remember it right away.
I called the number and a girl answered. She sounded like a teenager. I told her I had just missed a call from this number and she said she had not called anyone. I told her I thought I was calling my brother, M, back and she replied something like: "Sorry, you called my number, but this is April." I told her I was sorry to have bothered her and hung up.
I called my brother, J, and told him what had happened. After listening he said that he had tried to call and did not leave a message. J said the number I had called April on was M's old number that J had just cancelled. He asked me if I remembered a photo of M standing with a beautiful horse in a grassy field that had been taken years ago. I said I did. J told me that was the first horse M owned in Oklahoma and that her name was April.
After hanging up I checked my call history again. There was NO call received from M's old number, just my call to April.
There must have been something to this, but I have no idea what it is.
I'm fairly certain that your answers have ruled out any "mundane" reasons for the recording of your late brother's number on your phone.
For what it's worth, I agree with Haven that your late brother was trying to make contact, with the intent being to comfort you. It has been 21 years since my late brother reached out to me and I can tell you that my pain did reduce with time, but it is still there to remind me, from time to time.