The kanji and the radical are the same, so remembering the meaning of this kanji is as simple as making sure you know the radical for old first! If you know the radical, you know this kanji means old as well.
Note: This "old" does not refer to people. Think of it as "old things" instead.
Old things are misunderstood by the 子s (こ) of the world.
*Note:* Come up with a 子 character you can use for all the こ reading mnemonics going forward. This child will show up many times throughout your mnemonic journey, and it will help if you imagine the same character the whole time.