It's amazing how two very different views can be from the same family.
Growing up with divorced parents can cause some gaps in how things were between your parents. One parent says they tried to be there while the other, which is usually the one with sole custody, claims otherwise. When you have siblings that come from each parents' new relationships you start to feel pushed out and alone. Add to that the ten year age gap between the siblings and yourself and you start to have vastly different views on how each parent was. For instance, on parent may have barely been in your life for one reason or another and while you and your parent know this to be fact, the sibling may see it differently. This difference in views can often lead to conflict in that the child of that distant parent may feel offended especially if that parent was amazing to their child.
Additionally, that child only knows what it has seen and been told but because of the vast age difference there isn't a lot of first person for that child to go off of. Understandably it's hard to be in that position and learn that the man or woman you've looked up to may not be as fantastic to all as you thought. To learn that the parent you grew up with and learned from never really gave the other child that chance. Maybe the truth is that you as the first born to a torn home didn't know how to fit into either home as there was always one parent in each that you will never truly belong to. As an adult you can start to comprehend how it would be difficult to not show a difference when it comes to your flesh and blood and what you married into. There really is no blame in this situation because all you wanted to do was get out of a horrible relationship and move on but you can't with a child from that past relationship.
Regardless of how you look at it and from what view you see it from, that oldest child has a heck of a lot of hurdles both mentally and emotionally to jump over. It's not easy being put into their shoes either. You feel like you have no real home or anywhere you fit because you're only 50 percent of what the other child is. You're solely the responsibility of the one parent and while the other may try to hide the differences it still shows. To think it gets easier—it doesn't because with age comes cars, dances, babies, and weddings. There are financial aspects that just aren't feasible when one child is starting a family and may still need help and the other is starting to leave the house and become an adult. The financial aspect grows and this is when the differences really show. The oldest of the two houses kinda gets the shaft because the mom and dad have the other kids to worry about and their spouses want them focused on their collective kids, not the one they aren't responsible for.
Before you go feeling sorry for that oldest kid remember he or she has had to overcome things that most will never know about. This make that kid more equipped for handling things that come its way and deal with rejection and disappointment. The hardest part is that the siblings will never know the whole truth about what happened and a lot of the times the oldest don't either. So if you're in this situation or know someone who is, just remember that the life you had with your household is not the one they had. As happy and comfortable as you were growing up in that house, your big brother or sister could very well have felt like a stranger.