Xbox 360 Friend Request on Xbox One

Have you tried having him send you a friend request? This is some information I was able to find. It might be worth a shot to have him send you a friend request.

Viewing your Xbox One friends on your Xbox 360 friends list

With Xbox One, a friend is anyone whom you add to your friends list. Adding new friends on Xbox One does not require that they send a friend request first.

When you sign in to an Xbox One console, your Xbox 360 friends will automatically appear in your friends list, as well as your followers list. If you accept a new friend request sent from an Xbox 360 console, you will see them as a friend AND a follower
on Xbox One. However, friends who have been added on Xbox One will not automatically show up on your Xbox 360 list. If you plan to play with them on your Xbox 360, you’ll have to send a friend request through your Xbox 360 console. Once they accept, you’ll
then see them in your friends list on both of your consoles.

On the Xbox One, any friend requests will be followers if requested from a 360. They will show up as a follower until you add them back.

The 360 and Xbox One friend system seems to work in different ways. Try asking your friend to go onto his 360 (if he still has one) and accepting your request from there, or on the PC.

this may help

https://beta.support.xbox.com/help/friends-social-activity/friends-groups/view-xbox-one-friends-on-xbox-360

On Xbox One, a friend is anyone you’ve added to your friends list. Adding new friends on Xbox One doesn’t require that they send a friend request first.
When you sign in to an Xbox One console, your Xbox 360 friends will automatically appear in your friends list, as well as in your followers list. If you accept a new friend
request sent from an Xbox 360 console, you’ll see them as both a friend and a follower on Xbox One.

However, friends who’ve been added on Xbox One won’t automatically show up on your Xbox 360 list. If you plan to play with them on your Xbox 360, you’ll have to send a friend request through your Xbox 360 console. Once they accept,
you’ll see them in your friends list on both of your consoles.

If you go into the 360 game menu on the xbox one you may be able to see this.

https://www.youtube.com/watch?v=q7YhbokEf2U&feature=emb_logo

Are you on an xbox 360 and trying to add xbox one users? If so, once you send the friend request the user you are trying to add would need to view their friends list on xbox.com. There they will see your request under pending xbox 360 requests.

I had this issue as well when my friends switched from xbox 360 to xbox one, the one way i know to accept a friend request from xbox 360 to xbox one is to go on "xbox.com" and do it there or use the app.