He knows that I'm online on Whatsapp at night and will check my 'last seen' every night. Is this normal?

We haven't contacted or met for a year, but I just realised that he has been doing this for the past 2 months. Is this normal for a guy to do that? If so, what is his purpose?
He knows that I'm online on Whatsapp at night and will check my 'last seen' every night. Is this normal?
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