Is my not going alone to live with my elderly, difficult-tempered grandparents, to care for them when there is an aunt capable of doing so, considered disobedience to parents?

Serving parents when they are in need is obligatory upon children, and showing filial piety to grandparents is obligatory just as it is for parents. If the grandparents have no children except the questioner and her aunt, then both of them must cooperate in their care and be patient with them, while observing proper etiquette in their dealings, in compliance with the words of Allah Almighty: {And your Lord has decreed that you worship none but Him. And to parents, show good treatment.} The care of grandparents is obligatory upon their direct children, and if they refuse, then it becomes incumbent upon the more distant relatives. Accordingly, urging the aunt to undertake their care is obligatory. If she insists on refusing, then the questioner must undertake their care to the best of her ability, with the permission of her mother. It is preferable to combine their care with living with the mother.