twinkle in one's daddy's eye

Of a person, not yet conceived, particularly when referring to a time period preceding their conception.

Japanese Meaning

まだ受胎されていない人物、すなわち、受胎前の状態を示す表現 / これから生まれる子供、あるいは存在が計画されている（まだ受胎していない）人

When we bought that tiny house, our future son was still nothing but a twinkle in one's daddy's eye.

あの小さな家を買ったとき、私たちの将来の息子はまだ受胎していませんでした。

Sense（1）

Of a person, not yet conceived, particularly when referring to a time period preceding their conception.

Kid, I've been running fight outfits since long before you were a twinkle in your daddy's eye.

a twinkle in one's daddy's eye

（ canonical ）