@ernesjohnson I have 3 brothers and my relationships with each are vastly different. My older brother abused me physically and mentally for a large part of my childhood (it only stopped when I went to live full-time with my father) - we then had limited contact over the years, but for the last 5 or so years, I've essentially gone no-contact with him. He continues to have serious issues with his personal relationships, yet is gifted academically and is successful professionally. He is a nightmare to live with and his wife recently got the courage to end the marriage, after years of mental and emotional abuse, along with his constant infedility.
My brother who is 4 years younger than me (we have different fathers), is the one I have the most neutral/mediocre relationship with. We have some common interests, but otherwise have very different values. We don't fight or have any issues with one another, but we also are not really close; however, I do care for him. We don't spend much time together outside of special occasions, but I do spend more time with his son/my nephew as I offer to do occasional babysitting. I think he would be there to help me if I absolutely needed it, but he wouldn't be the first person I turn to.
My brother who is 11 years younger (different mothers) is the one I am close with; however our age difference means I always felt more like an Auntie than his sister, but it's been good that way. No rivalry/fighting/etc - if anything I've always been very protective of him; I see him always as the "baby", and just try to look out for him. We have similar personalities and just get along well; however, now that we are both adults, we each very much have our own lives. He recently moved to another state and has a goal to eventually move even further away for employment reasons- I know it will be even harder to see him than it already is. In an ideal world, I would like for us to live closer to each other, but I know that in today's world, people often choose to move away from family for a multitude of reasons (employment, romantic relationships or just pure desire to live in another locale!). It's simply not how it USED to be for many previous generations; my grandparents all had lots of siblings and they often settled nearby each other (even if they didn't get along) - there might be one odd sibling that lived out of the way, but many stayed close to the area they grew up in.
Even though I am close with one brother, I have no desire to have more children and raise them simultaneously! And based on my personal experience, one extra child wouldn't do the trick, I would need to have 3 (or more) to hope that my daughter MIGHT have a strong bond with one, the way I have with my youngest brother. I wouldn't care so much if I genuinely WANTED to have and raise a large brood (the hope for good sibling bonds would be secondary to my personal want for numerous children), but that desire is not there!! It's not guaranteed and I don't like the gamble. My daughter will be able to have a better quality of life by being my only. I don't feel guilty for "not providing a sibling" because she already has it better at 2.5 years old than I ever did!