TS, was your sister in law aware that you had plans to get married in 2010?
Para sa ako lang TS ha, there's no point in getting mad to what happened. Just leave it be, don't stress over it since it is totally out of your hands naman kung dili jud sila maminaw. But if you really want to resolve it, then ask for forgiveness and ask them to do the same and leave it all behind. Talk it over, invite them over if you have to and tell them you want to patch things up.