I will try to include as much information as possible to avoid dripfeeding so please bear with me.
I am in my mid twenties and currently live at home with my parents. I have one sibling who is late twenties, lives on their own. Sibling has been single for around 5 years, although has dated - which on several occasions has resulted in them unknowingly dating someone already in a relationship. My boyfriend is also in his late twenties, in the forces so lives on the base most of the week, we see each other when we can both during the week and at weekends. We have been together for around 2 years, so not a long time in the greater sense of things, but we are both committed to our relationship and talk about/are actively planning for the future.
As we don’t live on our own yet, it happens that my parents are around when my boyfriend is. They are happy with this, they have a good relationship with him and enjoy his company. Occasionally my sibling comes home for the weekend/dinner etc and has said in the past that they feel like a third wheel and that it’s weird how my parents like my boyfriend.
My boyfriend also came by for our Christmas lunch and they felt this was too much as it never happened during any of their previous relationships. Sibling also finds it “odd” and “uncomfortable” how my parents suggest the idea of a family get together i.e. lunch out and say quite openly that my boyfriend is invited.
I respect that my sibling may find this awkward at times as they are currently single however they are more than happy to benefit from my relationship when it suits them i.e asking to attend a work function as a guest of my boyfriend.
WWYD in this situation? I feel like piggy in the middle, especially as my sibling generally only talks about how they feel when we are alone - they have not mentioned it to our parents. I do think that bringing it up will be taken as an attack on the fact that they are not in a relationship which is not my intention, but I do feel that something needs to be said as ultimately I consider my boyfriend family - if we didn’t end up together in the long run, we would still be good friends.