I think I am bit hyper-aware of potential sibling issues since my siblings are like oil and water. I really want my kids to be friends, and actually like each other.
Good luck!
I'm aiming for my kids to love each other. They don't have to like each other, and from my own experiences with my siblings, I like them, but it's pretty obvious there are things about me that drive them crazy. We still hang out, but more importantly we try to keep in touch, we try to get our families together, and we work at our relationships, trying to assume little to nothing. We've got each other's back if one of us needs help or support in some way.
Of course it's partly just semantics, and you might mean the same thing, but we have to be clear with our kids and differentiate between the two so they know that it's ok to not want to do the same thing as the other sibling, and they might want a break from them, but they shouldn't be hurtful/mean, and if one of them is in distress they should treat it as important and step up to help where they can.
As part of that, I've had the conversation many, many, many times, and doubtless will continue to have it as each child grows. "Yes, he got more than you. How does that make you feel?" and eventually going through the process of helping them to understand that as they are each different, and at different stages of life, they will have different things, and sometimes they will perceive a disparity. Sometimes it attributable to their choices, sometimes it's an age thing (we get them nintendo portables between 5 and 8 years old depending on a variety of factors) and so one year you might see $130 gift in front of your brother, but that was what you got several years prior when they only got $50 worth of gifts. With the older kids we review budget principles and explain how we choose to allocate our limited funds for gifts. Sometimes it's simply how things worked out, and there's no root cause, but they can either accept it and enjoy the gifts they've received, or they can choose to be resentful and ruin their own day.
I don't know if this is a good way to approach it, but while I don't go out of my way to cause disparity, I also don't work hard to resolve disparity either. I suppose to some degree I'm teaching them to accept that life isn't fair...