You may need to have a tax professional review the deed.
In most cases, if you are a "remainder man" (or person), meaning you are a co-owner but someone else has a right of survivorship, that means you really aren't given anything of value until the person dies. (You couldn't sell your share of the house to a stranger, for example, while your mother was alive.) So the IRS considers that you inherited the property when your mother died in February and you would receive a stepped-up basis. The you and your siblings would report the sale as whatever your share of the sales price, and your basis is the same as the sales price, and you won't have a capital gain.
However, you may want to have someone review the deed in light of your state laws on property ownership to make sure the deed was prepared correctly. If not, you really will have a mess figuring out your basis.
