TL;DR: Tứ hành xung and lục hại are two ways of grouping the 12 earthly branches by convention in Eastern numerology, not scientific data about parent-child relations. Folk belief often uses them to say a child's zodiac clashes with parents, but Bát Tự and Tử Vi schools consider the whole four pillars or the whole chart, not just the birth year branch. It should be treated as cultural reference, not used to decide whether to have a child or to judge family affection.
What are tứ hành xung and lục hại in the system of the 12 zodiac animals?
Tứ hành xung is a way of grouping the 12 earthly branches into three sets of four: Dần, Thân, Tỵ, Hợi; Tý, Ngọ, Mão, Dậu; Thìn, Tuất, Sửu, Mùi. Lục hại is six pairs of branches considered to harm each other: Tý harms Mùi, Sửu harms Ngọ, Dần harms Tỵ, Mão harms Thìn, Thân harms Hợi, Dậu harms Tuất. Both are conventions of Eastern numerology, formed from the earthly branch system tied to the five elements, yin and yang, and cardinal directions, not from any study of family relationships.
The book Đẩu số tinh thành sets out the branches in the usual way: Tý, Dần, Thìn, Ngọ, Thân and Tuất are yang; Sửu, Mão, Tỵ, Mùi, Dậu and Hợi are yin; Dần and Mão belong to Wood, Tỵ and Ngọ to Fire, Thân and Dậu to Metal, Tý and Hợi to Water, Thìn, Tuất, Sửu and Mùi to Earth[1]. It explains lục xung as two branches facing each other in direction: Tý and Ngọ, Sửu and Mùi, Dần and Thân, Mão and Dậu, Thìn and Tuất, Tỵ and Hợi[1]. Each tứ hành xung group is made of exactly two of these lục xung pairs, that is, four branches evenly spaced around the circle of twelve. So within a group not every pair overcomes the other in the five elements: Dần (Wood) and Tỵ (Fire) are Wood generating Fire, and Thìn, Tuất, Sửu and Mùi all belong to Earth.
A distinction is needed: tứ hành xung is a relationship among branches within the same group, whereas lục hại is a pairwise relationship. A person born in the year of Dần, for example, is in the same tứ hành xung group as Thân, Tỵ and Hợi, and harms Tỵ under lục hại. So one zodiac year can both clash and harm another, or only clash without harming.
Why does folk belief say a child's zodiac year clashes with the parents'?
This saying is widespread in Vietnamese families, especially when preparing to have a child or when there is discord in the household.
People believe that if a child is born in a year that clashes with the father's or mother's, the family is prone to discord, the child is hard to raise, business is unsettled, or the parents struggle because of the child. This belief is passed down orally and is sometimes reinforced by people who read ages and by folk books with vague interpretations.
However, it should be clearly seen that this is a belief, not a law of nature. The earthly branch system itself was originally a tool for recording time, not something created to assess affection or fortune between people. Assigning a meaning of "clash" to a pair of zodiac years is a later cultural interpretation, not part of the original definition of the earthly branches.
Do the specialist schools agree with judging a child's zodiac year as clashing with the parents'?
Bát Tự and Tử Vi do not judge the relationship between parents and children from the earthly branch of the birth year alone. Bát Tự examines all four pillars (year, month, day, hour) with the full set of heavenly stems, earthly branches, five elements and generating and overcoming relationships; Tử Vi examines the entire chart with its palaces and stars. Taking only the birth year to conclude a clash leaves out most of the data that these very disciplines consider necessary.
In Bát Tự, relationships among branches are examined at many levels: clash, harm, punishment, destruction, combination, triple combination, half combination. The earthly branch of the birth year is only one of the eight characters of the chart. The same Dần year with different birth months, days and hours already interacts differently with the parents, so attributing a clash or not from a single year branch alone lacks basis.
In Tử Vi, the relationship between parents and children is examined through the Phụ Mẫu (Parents) palace and the Tử Tức (Children) palace, together with the stars and their states of miếu vượng and hãm địa. Đẩu số tinh thành gives the example of the Mệnh palace in lục hợp with the Phụ Mẫu palace: one's relationship with one's father is close, a good Phụ Mẫu palace means a good relationship and a bad one means a poor relationship[1].
Introductory books may list clash and harm tables for learners to memorise, but when making a judgement the whole picture is considered.
Reference table of tứ hành xung and lục hại by the 12 zodiac animals
Below is a reference table for quick lookup. The "Tứ hành xung" column lists the zodiac years in the same clash group as the year in the first column; the "Lục hại" column lists the directly harming year.
| Zodiac year | Tứ hành xung (same group) | Lục hại |
|---|---|---|
| Tý | Ngọ, Mão, Dậu | Mùi |
| Sửu | Mùi, Thìn, Tuất | Ngọ |
| Dần | Thân, Tỵ, Hợi | Tỵ |
| Mão | Dậu, Tý, Ngọ | Thìn |
| Thìn | Tuất, Sửu, Mùi | Mão |
| Tỵ | Hợi, Dần, Thân | Dần |
| Ngọ | Tý, Mão, Dậu | Sửu |
| Mùi | Sửu, Thìn, Tuất | Tý |
| Thân | Dần, Tỵ, Hợi | Hợi |
| Dậu | Mão, Tý, Ngọ | Tuất |
| Tuất | Thìn, Sửu, Mùi | Dậu |
| Hợi | Tỵ, Dần, Thân | Thân |
The two lục hại pairs Dần and Tỵ, Thân and Hợi fall within the same tứ hành xung group. Conversely, Dần and Hợi, Tỵ and Thân are in the same tứ hành xung group yet form lục hợp pairs, so the same pair of ages can count as combining in one table and clashing in another.
Common misunderstandings when judging a child's zodiac year against the parents'
The first misunderstanding is thinking that looking up the birth year is enough. In reality, the same birth year with a different month, day or hour means the earthly branches of the month, day and hour already create a different interaction. Bát Tự examines all four pillars, so a conclusion from the birth year alone is insufficient.
The second misunderstanding is equating "clash" with "overcoming" in a bad sense. Đẩu số tinh thành writes that lục xung carries the sense of stirring into motion, and that in Tử Vi đẩu số, whether a star is good or bad, without a clash it does not move, and only when it moves do good and bad show[1]. Folk belief tends to assign a negative meaning straight away, while specialist books consider many more factors.
The third misunderstanding is using tứ hành xung to decide not to have a child or to choose the child's birth year. This applies a lookup convention to a momentous decision without any scientific basis. Researchers on marriage and family do not use the earthly branch of the birth year to predict parent-child relationships.
The fourth misunderstanding is confusing lục hại with tứ hành xung. The two tables are different, with different scopes. Some people look up the wrong table and then draw the wrong conclusion.
How should this knowledge be understood and used sensibly?
A sensible understanding is to see tứ hành xung and lục hại as part of the lookup culture of earlier generations, helping to explain why folk belief has sayings about zodiac years, but one should not treat them as true or false predictions about family affection.
In specialist practice, if one wants to judge parent-child relationships by Bát Tự or Tử Vi, the full birth date and time are needed and all factors must be considered together. Even then, the result is only an interpretation under one system of conventions, not a scientific conclusion.
Nhật Nguyệt's suggestion: if someone in the family is worried because a child's zodiac year clashes with the parents', it should be seen as an occasion to learn about traditional culture, and it should not be allowed to influence the decision to have a child or how to treat the child. To see which table a particular birth year falls under with the father's and the mother's ages, the Child's birth year by parents' ages tool keeps the stem, zodiac and nạp âm axes separate, without adding up scores. Family relationships depend on upbringing, communication and love, not on the earthly branch of the birth year.
