Why Lord Rama Had Three Brothers

We saw that there are several versions of why Lord Rama took avatara on earth as a human being.
Also, the exact context when Sri Hari was requested by Devas to take avatara on earth.
Here is the version as per Valmiki Ramayana.
Dashrath’s Ashwamedhayaga and Putreshti were going on.
A lot of devas had assembled there.
To receive their shares of the offerings made in the yajna.
At that time they complained to Brahma
Because of the boon given by Brahma, Ravana has been committing a lot of atrocities and has made life difficult in all the worlds.
That time Brahma said, I have only given him a boon that he can not be killed by Devas, Gandharvas.
He didn’t include humans in that list because he never asked for it.
He thought, anyway humans are weaklings, even without the boon no human can touch.
That means Ravana can be killed by a human being and only by a human being.
When this conversation was going on, at that time Bhagawan Vishnu came there, holding shankha, chakra, and gada in his hands.
Brilliant, wearing peetambara, mounted on Garuda.
To the Lord the devas told: we are prompting you, requesting you to divide yourself into four and take birth as the sons of this Dasharatha who is desirous of children, who is conducting this Putreshti for that.
This is a request, a prayer because Devas praised him before that.
They bowed their heads before him.
So, they are not equals.
Sri Hari and the other Devas are not equals because before making this request, they bowed before him and praised him.
You should take birth as the sons of Dasharatha and his three wives.
They are well qualified to be parents of your human birth.
Dashratha is a king, he knows dharma, he is a scholar.
If you look at him, he has the tejas of a Maharshi.
And his three wives, they can be compared to Daksha kanyas: Hree, Sree, and Keerthi.
Why is this necessary?
Because there is this Ravana who is so cruel and arrogant.
He kills Rishis.
He kills Gandharvas and their wives apsaras who are looking after their own businesses and playing in Nandana Vana, the garden of Swarga.
Not just us Devas, but for all of us including Munis, Siddhas, Gandharvas, Yakshas. you are the last resort.
Please be born as a human in Manushya Loka.
In fact, the prayer is to be born as four – the Chatur Vyuha – Rama, Lakshmana, Bharata, and Shatrughna.
Why as four, why not one?
Because there were four distinct roles:
Killing of Ravana.
The killing of Ravani, Ravana's son, Indrajit.
Conquering the Gandharva kingdom which was done by Bharata.
The killing of Lavansura which was done by Shatrughna.
Each of these tasks had its own specific demands.
That’s why the Lord took avatara as four.
Then the Lord told:
Don’t be afraid anymore, I am going to kill that cruel Ravana along with his sons, grandsons, relatives, and friends.
Then I will stay here as a king and re-establish dharma which has been disturbed by Ravana.
This will be for 11,000 years.
Thus the Lord desired, that let me take birth as the four sons of Dasharatha.
The Lord is Jagat pita, father of all.
In that sense, Dasharatha is his son.
Let me take birth as the sons of my son here, Dasharatha.
Because it is for the welfare of the world.
He is without birth and death.
Only the created shareeris such as Men, Devas, Asuras, plants, and animals, they only have birth and death.
But here, the Lord desired to be born as one or four with definite beginning and end.
For the welfare of the world.