Legal Question in Wills and Trusts in California

Off the top of my head, I cannot think of any ethical or legal barrier to him representing you in general, however, there could be specifics of the situation where it might be ethically questionable. For example, if he gained confidential information in representing your husband that would give him an unfair advantage in a contested probate in which your interests would be contrary to your husband's will, that could present problems. In any case there would be no harm in asking him to represent you and letting him run his own conflicts check before accepting the representation.