房分是家族發展過程中較為普遍的現象，其基本原則是父子對立、兄弟對等。唐代房分是父系繼嗣體系，房支絕嗣後，通常都是由同宗中昭穆相當者承繼，這與陳其南所討論的房不同。房支間關係高下相懸，普通房支逐漸衰退，促進了家族內部的分化與瓦解。另一方面，房還具有擴展性的特點，對家族有一定的整合作用。唐代保留了魏晉南北朝大家族的觀念，崇尚著房，重視著房號，有些房號還具備了標榜門第的功能。家譜的編撰也受到房分作用的影響，唐代的家譜有依房支編撰的支譜，這與小家族從大家族中逐漸分離的趨勢相一致，也有將同姓的遠房支系合編為譜的通譜，而這所反映的是魏晉南北朝以來的門閥大家族觀念，但是這種同譜關係較為鬆散。從譜牒上看，唐代的家族仍然規模龐大，但事實上卻是支系林立，各自為房的小家族，反映了唐代家族由門閥大族向宋以後家族轉型的過渡性特點。

Fangfen, the principle of equality among brothers, was a very common phenomenon in the process of family development. The patrilineal system in the Tang Dynasty was based on the principle of filiation. When a family had no descendent, it usually chose an heir from the same clan; the concept of fang adopted here is different from the one used by Chen Qinan. The great difference in the strength of different fangfen branches usually led to a general decline of the subsidiary branches; this in turn contributed to the division within the family. On the other hand, fangfen also provided an integrative force to the family. The Tang Dynasty retained the large family concept of the Wei, Jin, Southern and Northern Dynasties, upholding the main branch and its name. Some of the fang even served the function of the boasting of status. The compilation of genealogies was also affected by the function of fangfen. In the Tang Dynasty, although there were genealogies that included different fang branches, coinciding with the trend of family division, there were also compilations of genealogies for distant relations of the same surname. This reflects the dominance of the idea of the rich and powerful clan since the Wei Dynasty. Yet this arrangement in the genealogy showed a loose relations between the families. The genealogical records of the Tang Dynasty show that the family size was still large but with numerous subsidiary branches, being smaller families of their fang. This reflects transformation of Tang Dynasty families from rich and powerful clans to the family system of the Song and later dynasties.