Nuclear family vs Joint family

Question

A married couple of male & female with their children is consider a social unit.
A single social unit staying independently -- is called "Nuclear family" and when multiple such units stays together depending on each other -- is called "Joint family".

According to AnushAsana Parva and Manusmruti, a woman should be always protected by father during tender age, husband after marriage and children during old age.
Hence whether a family is "nuclear" or "joint" is decided based on where the man is staying. He may stay with his father &/or brother.

What do dharma shAstra talk about whether a married man should stay with and for how long?
As that decision will eventually lead to nuclear or joint family.

_{Note: Gita is neutral on this topic. It usually says that a person seeking liberation would be away from the crowd, physically or mentally. However, that's a special case & hence answers from Gita may not fit here.}

Answer 1

Hindu scriptures prescribe the joint family lifestyle.

To my knowledge there are no explicit verses in the Smritis which say that one must live jointly but several verses can indirectly be interpreted leading to that conclusion.

Manu Smriti 2.227. That trouble (and pain) which the parents undergo on the birth of (their) children, cannot be compensated even in a hundred years.

Manu Smriti 2.235. As long as those three live, so long let him not (independently) perform any other (meritorious acts); let him always serve them, rejoicing (to do what is) agreeable and beneficial (to them).

Manu Smriti 2.236. He shall inform them of everything that with their consent he may perform in thought, word, or deed for the sake of the next world.

These above verses are hinting towards all sons staying with parents lifelong.

Manu Smriti 3.116. After the Brahmanas, the kinsmen, and the servants have dined, the householder and his wife may afterwards eat what remains

3.116 is saying that the husband and wife should dine only after the relatives (Svayeshu in the original text) have already dined. This is clearly talking about a joint family.

Manu Smriti 2.132. (The feet of the) wife of one’s brother, if she be of the same caste (varna), must be clasped every day; but (the feet of) wives of (other) paternal and maternal relatives need only be embraced on one’s return from a journey

Now, clasping the feet of the wife of one's brother is possible only if the families are staying together.

The Vedas too clearly advocate the joint family system:

In the Atharva Veda (denoted by AV in this answer), there is Concord Hymn, which talks about maintaining unity and concord in a joint family.

The union of hearts and minds, and freedom from hate i'll bring you. Love one another as the cow loves the calf that she has borne. AV 3.30.1

Let not a brother hate a brother, nor a sister hate a sister; unanimous, united in aims, speak you words with friendliness. AV 3.30.3

Having superiors who are conscious (of their tasks), be not divided. Thriving together, moving on with joint work, come speaking sweetly to one another; I'll make you have one aim and be of one mind. AV 3.30.5

I will make the prayer, for that concord among men at home, by which devAs are not apart from them, so that none hates the other. AV 3.30.4

Common be your water-store, common your share of food. I bind you together to a common yoke. United, gather round Agni, the spokes around the nave of a wheel. AV 3.30.6

The bride's role in a joint family is explicitly stated in the following mantra:

samrAjnedhi svasurishu (1),
SamrAjnuta devrushu (2),
NanAndu samrAjnedhi (3),
SamrAjnuta svasravAha (4).

............

Be a queen to thy father-in-law (1), a queen to thy brothers-in-law (2), a queen to thy husband's sisters (3), a queen to thy mother-in-law (4).

AV 14.1.44

Note that SamrAjni= Queen. So, the mantra is asking the bride to be like a Queen (means very dear) to her in-laws.