Arenaria is a genus of flowering plants, within the family Caryophyllaceae.
Sciadopitys verticillata, koyamaki, or Japanese umbrella-pine, is a unique conifer endemic to Japan.
 It is the sole member of the family Sciadopityaceae and genus Sciadopitys, a living fossil with no close relatives, and known in the fossil record for about 230 million years.

Question: Are Arenaria and Sciadopitys verticillata part of the same family? 
Answer: no