I don't think you are being unreasonable at all. I kind of experienced this with my exH. My ex is this way with his sister. My friends who have known his since high school as I have find it kind of weird. She has always said "jump" and he says "how high?"
Whatever she wanted she got without hesitation, I asked for the smallest thing and he would moan and groan.
Do you feel he would do the same for you as he would for her?
Does he feel like he "owes" her something?
I really think you should bring up your concerns and your feelings. HIs reaction and explanation will probably tell you a lot.
For your future, I do think this is worth addressing and I hope he gives you some comfort clarity, and understanding on this.
