Who is Agastya's brother in the Ramayana?

Question

In the Aranya Kanda of the Ramayana, Rama, Lakshmana, and Sita are on the way to the ashram of the famous sage Agastya when they first stop by at the ashram of another sage:

While viewing beautiful forests, cloud-like mountains, lakes, and rivers that are flowing following the pathways, Rama happily journeyed on the pathway indicated by sage Suteekshna, then he gladly spoke this sentence to Lakshmana. "Definitely this alone appears to be the hermitage of Sage Agastya's brother, one with great soul and pious deeds. As how thousands of trees are bowing under the weight of flowers and fruit on the pathway, thereby I perceive it to be the hermitage of Agastya's bother." ...

Raghava spent one night there when that sage received him well and when they dined on tubers and fruits. Raghava spent that night there and when sun rose in solar orbit he took leave of the brother of Sage Agastya saying the following. "Oh, godly sage, we stayed in the night comfortably, I now make an obeisance and bid farewell to you, as I wish to proceed to see your mentor and elder brother Agastya. When the brother of Agastya said, "you may go," Rama the legatee of Raghu journeyed on the pathways as directed by Suteekshna[.]

My question is, who is this brother of Agastya that Rama visits in the forest? As I discuss in this answer, the sages Agastya and Vasishta are the sons of Mitra god of friendship and Varuna the ocean god. Here is how the Srimad Bhagavatam describes their birth:

Agastya and Vasiṣṭha Ṛṣis were the common sons of Varuṇa and Mitra, the tenth son of Aditi. Upon seeing Urvaśī, the celestial society girl, both Mitra and Varuṇa discharged semen, which they preserved in an earthen pot. The two sons Agastya and Vasiṣṭha later appeared from that pot, and they are therefore the common sons of Mitra and Varuṇa.

Clearly the sage Rama met wasn't Vasishta, since Vasishta lived in Ayodhya. So how could Agastya have another brother? Would he also be a son of Mitra and Varuna, and if so how was he born?

The Ramayana translator just says this:

The name of this brother of Agastya is Sudarshana. But none calls him by that name and he is just called agastya bhraata, Agastya's brother.

So are there any other scriptures that discuss Agastya's brother Sudarshana? And what text gives his name as Sudarshana?

EDIT: I found this chapter of the Setu Mahatmya of the Skanda Purana describes the death of Agastya's brother. In this account, Agastya's brother prays to Shiva for Moksha, and Shiva appears before him and tells him to bathe in the Amritavapi Tirtha, located in what is now the Ekantharama Temple near Rameshwaram. He does so, and he attains Moksha. But the Skanda Purana doesn't provide any biographical information about him, just that he is the "brother of the Pot-born Sage". So I'm still trying to find how Agastya, being born in a pot along with Vasishta, could have an additional brother.

Answer 1

I did not find any detail on Sudarshana but I did stumble across this information regarding a different brother of Agastya hence sharing it. Shrimad Bhagvatam Chapter 4 Verse 1.36 mentions the following about the birth of Agastya:

TEXT 1.36

pulastyo 'janayat patnyām
agastyam ca havirbhuvi so
'nya-janmani dahrāgnir
viśravāś ca mahā-tapāh

pulastyaḥ - the sage Pulastya; ajanayat - begot; patnyām - in his wife; agastyam - the great sage Agastya; ca - also; havirbhuvi - in Havirbhū; sah - he (Agastya); anya-janmani - in the next birth; dahra-agniḥ - the digesting fire; visravāḥ - Viśravā; ca- and; mahā-tapāḥ - greatly powerful because of austerity.

TRANSLATION

Pulastya begot in his wife, Havirbhū, one son of the name Agastya, who in his next birth became Dahrāgni. Besides him, Pulastya begot another very great and saintly son, whose name was Viśravā.

The Vishnu Puran Chapter X also mentions him being born to Pulatsya which would again testify to his kinship with Vishrava:

The wife of Angiras, Smriti, bore daughters named Siniválí, Kuhu, Ráká, and Anumati (phases of the moon). Anasúyá, the wife of Atri, was the mother of three sinless sons, Soma (the moon), Durvásas, and the ascetic Dattátreya. Pulastya had, by Príti, a son called in a former birth, or in the Swáyambhuva Manwantara, Dattoli, who is now known as the sage Agastya.

It may be possible that the rishi mentioned in Rama's meeting with Agastya's brother could actually be Vishravas who BTW was his enemy's father and the omission of his name may actually be intentional!

Answer 2

Based on text and internal astronomy evidence, I have been able to date VR to 12,000 BCE. It is the time when the star Abhijit, Vega was in the northern direction. Shloka:

brahma rāśir viśuddhaḥ ca śuddhāḥ ca parama ṛṣayaḥ | arciṣmantaḥ prakāśante dhruvam sarve pradakṣiṇam || 6-4-49|| Brahma Rashi identified as Abhijit. Confirmed from shloka:

atha pavana samāna vikramāḥ plavaga varāḥ pratilabdha pauruṣāḥ | abhijit abhimukhām diśam yayuḥ janaka sutā parimārgaṇa unmukhāḥ || 4-63-15

Stars Abhijit (Vega) and Agastya (Canopus) are situated diametrically opposite with respect to the eplictic plane. When Abhijit is located in the northern direction Agastaya must be in the southern direction.

Rama meets Agastya bhrāta in one evening and the next evening sage Agastya himself in his ashrama. Both are situated in the southern direction. One of the incidences is sighting of the Agastya the southern polestar of those times.

The first meeting could be seeing the star in the sky, and the second meeting with Agastya muni or his descendent carrying the lineage of Agastya muni forward. The text does not say explicitly so.