Yes, this is perfectly legal, and common enough that there is a name for it: "life estate." The seond wife is given a "life estate" which lets her possess and reside in the home for her life; the son gets a "remainder" interest (he is called a "remainderman"), which means that the home becomes his on her death. Your brother should let an attorney (e.g. a trusts and estates attorney) draft the will for him, to make sure it is phrased correctly, but this is definitely something he can do.