We are a real blended family. Dh has two dc from his first marriage and I have two dc from mine. We also have one dd between us. We always treat all 5 dc the same as each other and we expect other family members to do the same.
Mil is starting to drive me mad though. She quite obviously treats my elder two children differently from the other 3 who are biologically her grandchildren.
It's only ever small things but they start to build up over time. At Christmas she was lining up the three girls to take pictures and wittering on about how lovely they all looked. Whereas my 2 were just ignored. And she is always really interested in what they have been up to but she barely asks my elder 2 a single question. Also we sent her pictures of the kids and she has only put the ones out of the 3 girls. Dh is prepared to speak to her but I need to check we aren't overreacting? My elder dc are 10 and 12 so they really notice things