I feel totally nauseaus reading that. Their cruelty will come back to haunt them one day. Not only did the elders treat him badly but the siblings allowed it to happen and did nothing to stop it. I don't know which was worse. To think this is actually some kind of loving discipline and kindness
Please extend my condolences to your cousin.
Perhaps make time for the two of you to sit and have your own rememberance of her and to separate his sense of loss from his sense of outrage at such horrendous treatment by the elders and his siblings.