I’m unable to figure out a passcode on an old phone

If your device has iOS 15.2 or later installed, you can reset it without a computer; check out this link→How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support. Otherwise you will need a computer:

See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After restoring the phone using one of the methods above you can restore your most recent backup.

Lillianfrom Said:

"I’m unable to figure out a passcode on an old phone: My brother had an old phone and we’re trying to transfer it to a family member and we no longer remember the passcode"

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Properly Transferring an iPhone:

Once all is accessible, you should perform as instructed here, including the backup creation, and iCloud logout: What to do Before you Sell, Give Away, or Trade In your iPhone or iPad - Apple Support

What does your reply have to do with a forgotten passcode?

Lawrence Finch Said:

"What does your reply have to do with a forgotten passcode?"

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As the OP Reads: "we’re trying to transfer it to a family member"

Trying to transfer the iPhone, which is disabled, to another person. Not trying to transfer data to another phone.