Is 2 years enough time to date again if a partner dies?

It's been now 2 years since my brother's long-term girlfriend died.

He's still taking his time though. Would you say 2 years is enough time for him to date again?

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+1 y
Sometimes he still gets depressed that he never got a chance to propose to her after getting off work that day. He had to sadly return the ring.
Is 2 years enough time to date again if a partner dies?
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