Casey

In 2018, 20 is the most common age for an American (U.S.) Casey who is registered male with the Social Security Administration. It is the 484th most common male first name for living U.S. citizens.

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In 2018, 23 is the most common age for an American (U.S.) Casey who is registered female with the Social Security Administration. It is the 638th most common female first name for living U.S. citizens.

Kaicie is a rare spelling of Casey.

Casey and Kasey are probably the only variants for both boy and a girl. Kacie Kasie Kacey are not unisex.

The name Casey was given to 325 girls born in the US in 2016.
65.06 percent of people with the first name Casey are male.

I believe Casey is the best spelling for a boy. The others are for the girls.