Is loving one's stepmother considered disobedience to one's parents, and is a person sinful for having this feeling as long as they do not express it or translate it into actions?

Love is a great malady. If this love is not sought by you and you do not wish for its fulfillment, then we hope that you will not be sinful merely by its presence and that it will not be considered disobedience to parents. Masturbation is forbidden (haram), and its prohibition is intensified if it involves imagining your father's wife. Masturbating by thinking of a forbidden woman is forbidden; rather, it is akin to fornication, for the heart yearns and desires. Fear Allah and strive against this love, seeking assistance from her Creator. Beware of being alone with this woman and treat her as if she were a stranger to you. Indeed, there is scholarly consensus on the prohibition of looking at a strange woman or one of your unmarriageable kin (mahārim) with lust.