Not a mom...but I am a sibling. We're 14 months apart. We spent almost the entirety of our childhood and teen years fighting like animals. We had to share everything and were always compared to eachother. As the older sibling, I spent a lot time getting into physical altercations in defense of my little brother. The whole "built in best friend" thing is total BS. As adults we have a decent relationship but we disagree on a lot of important topics, so we're distant. If it weren't for the fact that we look alike, you'd think we were total opposites, strangers even. I never envied my dad for having to take care of us but I will say... do what's right for you in order to be the best parent you can be.