If you have not spoken to the attorney that assisted with the estate, it would be advisable in regard to the provision about the three brothers getting an equal share of the house.
As it has been described, it seems that you and your brother were each gifted one third of the house ten years ago. But, that means there was only a one third owner share to be split three ways by the will.
A one third share equally split is a one ninth share which is the portion the third brother was willed.
State law, rather than the federal tax code, is what determines how ownership interest is determined and when it passes.
When property is inherited, the beneficiary can use the market value on the date of death as the cost to figure gain or loss on the sale. For example, the 300K value house bought for 60K that is willed to three brothers would use the 300K and figure and gain or loss using that amount. Selling that house for 300K results in zero gain for the three brothers.
When property is gifted, the recipient uses the cost of the donor to figure the gain or loss. A house bought for 60K would use 20K for the value of the gift of one third of that house. If that house was sold for 300K each one third owner would have 80K of taxable gain (100K-20K = 1/3(300-60)).
Both gift and inheritance can happen to the same house. Using the same values in the above example (300K at date of death and 60K cost), after gifting away two thirds if one of the one third owners wills her share to three others only her one third gets raised to the fair market value at date of death.
In that case there is one third valued at 100K and the other two brothers have a one third with cost of 20K at date of death. For figuring gain the 100K is split between the three heirs so the out of state brother has a one ninth interest in the house with cost of 33.3K ( 1/3 of 100K) and the two brothers that had gifts have 53.3 K cost on what is now a 4/9 share of the house.
For a sale at 300K, the gain reported would be zero for the out of state brother. (1/9 of 300K= 33.3K sales receipt and 33.3K cost)
For the sale at 300K the gain reported by each of the brothers that had a gift of one third would be 80K (4/9 of 300K = 133.3K sales receipt and 53.3K cost (20K from gift plus 33.3K from inheritance).
Of course, the brothers with the one third gift share may still decide to give the out of state brother one third of the total receipts (1/3 of 300K) but the that does not change the tax consequences of having received one third of the house as a gift and being required to use the donor's cost to figure gain on the sale.
Sorry this is as simple as it can be demonstrated; so several items have been left out of the example. Costs of selling (and taxes) would reduce the 300K receipts and reduce the gain of each brother (even possibly creating a loss for the out of state brother).
Additional cost or improvement may have happened after the one third gift and that cost would add to the one third of the donor cost of 20K and would reduce gain.
Depreciation that was allowed while the property was rented would reduce the cost basis and increase the gain.
There is much to consider in this situation; so please ask if you need clarification.