Psi Upsilon IV

From Memory Alpha, the free Star Trek reference

Psi Upsilon IV was the fourth planet in the Psi Upsilon system, and was inhabited.

Daniel Kwan, half-Human half-Napean son of Ronald and Emiraa was born on this planet, on stardate 40004.3. (TNG: "Eye of the Beholder")

Some speculate this may be the Napean homeworld, but there is no proof to substantiate it.

An okudagram readout of Kwan's personnel file was displayed on a viewscreen that Deanna Troi was studying. Some of the facts could be called into question since she was involved in a very detailed hallucination when the data was shown. This could explain why the stardate indicates he was only seven years old at the time of the episode.