It is about my cousin not grandparents......my grandparents never abused me just disowned their granddaughters?

You will never know what they are thinking or why they have made the choices they made unless you summon up the courage to have a face to face and ask them. Don't waste your life thinking you know the reason they do or have done something and end up losing precious time you could have spent with them. Talk to them. Invite them to lunch, your treat and talk. Worse case scenario, they are monsters and you at least got to eat a good meal. Best case, you mend the fences before too late.