Dought & clear - , Deciding on profit shares in a joint venture may be according to what the two partners agree on, not commensurate with each partner’s contribution to the capital.

What is the Islamically acceptable way to share the profits in a
business partnership involving two men who are doing business with
capital of 3 million liras, 2 million from one of them and 1 million
from the other?
Praise be to Allaah.
The scholars (may Allah have mercy on them) differed concerning howthe
profit is to be shared: should it be commensurate with each partner's
contribution to the capital, as in the case of loss, or should it be
according to what is agreed upon between the partners, whether it is
great or small? There are two opinions:
1. The view of the Hanafis and Hanbalis: that the profit should be
shared according to what the partners stipulated and agreed upon, so
long as the profit is clearly defined.
2. The view of the Maalikis and Shaafa'is: that the profit should be
shared commensurate with each partner's contribution to the capital.
Ibn Qudaamah (may Allah have mercy on him) said: It is permissible to
share in profit according to the share contributed by each partner, and
it is permissible to share it equally, even if their contributions
differed, and one may take more than the other even if their
contributions wereequal. This was stated byAbu Haneefah.
Maalik and ash-Shaafa'i said: One of the conditions of it being valid is
that profits and loss must be commensurate with the proportion of
capital contributed, because profit in this partnershipis connected to
the capital.
In our view, work (done by one of the partners) deserves a portion of
theprofit, so it is permissiblefor them to have different levels of
profit if one of them is putting work into the business, as when
different people use the capital ofone man for business (mudaarabah).
That is because one of them may have more experience in business than
the other, and may be more able to achieve results. So it is permissible
for him to stipulate an additional share of the profits in return for
his work, as a proportion of the profit may be stipulated in return for
the work of the one who is running the business venture.
End quote from al-Mughni (5/19).
Based on that, the profit may be divided in the following manner:
The one who contributed 2 million is entitled to two thirds and the one
who contributed 1 million is entitled to one third. This is according to
the Maaliki and Shaafa'i madhhabs, and is a fair division that is valid
according to scholarly consensus.
If the two partners agreed not to divide the profit according to the
proportion of the capitalcontributed by each, andthey want - for example
- to divide it between them in two equal halves, so that the one who
contributed 2 million takes half of the profit and the one who
contributed 1 million takes the other half, and they both agree to that,
then this is also permissible according tothe Hanafi and Hanbali
madhhabs, because it is their right to decide, and the one who
contributed the greater part of the capital may yield a portion of his
profit to his partner, voluntarily.
Shaykh Ibn 'Uthaymeen (may Allah have mercy on him) also stated that the
latter way of sharingthe profit between two partners is valid. See:
ash-Sharh al-Mumti', 9/403
And Allah knows best.