A male coworker I kind of like is coming to my birthday party and I want to see if he potentially feels the same, how should I go about doing that?

He is willingly coming even though he could be the only guy there. At work, we laugh all the time, he has held the door open for me, he asked someone how I was doing shortly after I left, a flower fell on the ground and he said "want a flower?" I am just curious if the feeling is mutual and how I should find out without asking directly.

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I am his boss I forgot to add
A male coworker I kind of like is coming to my birthday party and I want to see if he potentially feels the same, how should I go about doing that?
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