actually once the husband is dead , there is no relation imposed on the widow, she doesnot have any relation with the mother father brother sister of the deceased husband. so devar bhabi marrige doesnt come here!! whatever may be the intention or the hiddent feelings, whatever that mayb e but the relation was over once the husband dies.
there was also a movie of sunny deol mahima and pardes guy, he loves mahima, get married , finds out bro loves his wife, fakes his death, mahima marries sunny ( as after death no realtion of jeth bhabi,) he ocmes back but sunny dies in a fight and mahima is again with pardes guy. my point is that adfter death there is no relation of inlaws, legally and in religion.