Am I wrong to feel like an outcast

I have a question. I want to know what others would feel or do in this situation

I was adopted as a infant. I am now 56. When I was in my early 20s I located my biological family. I found both parents (married to each other) and 7 siblings. Over the years I have developed bonds with our mom and most of the siblings. I was close to our dad up to his passing. Recently our mother passed away. At her memorial I was told that I wasn’t wanted there. And that one of my sisters wished I hadn’t come. Afterwards they all got together and did a lantern release for our mom. Me and my family were not invited. When I asked my sister about it I was told it was for moms “real” children only. I feel pushed aside and left out. She never invited us to family functions and basically has always been stand offish. I am rather upset and feel unwanted. Am I justified to feel the way I do? I was quite close to our mom and spent lots of time with her and even went on several trips with her. But I feel my sister wishes I wasn’t around. And to my face she says she loves me. One of my other sisters doesn’t understand why this is happening either.