Yes, the mother obviously retained a life estate (of some type, depending upon state law).
However, it matters as to how the deed was drafted when the brothers received a share (which, presumably was one-third between the three). If that were the case, then the mother would be entitled, by default unless provided otherwise, to a share of the proceeds from the sale.
Of course, the brothers could report the entire amount of the proceeds from the sale (one-half each) if that was the prior arrangement.
