How can someone know about my 2nd account

Hi Everyone,
I have 2 accounts on twitter. I was banned from following an individual on my main account. I have a 2nd account that i created but have never used for anything. No follows/ers or tweets.
I just noticed that this individual has also blocked this 2nd account. My question is how could they even know it existed?? How would they find this info?
CHeers in advance,

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