I come from a relatively big family, including three brothers and a sister. So when my husband and I first started talking about having kids, I figured:"I liked the way I grew up, so let's have five!" Turns out, kids are expensive AF (who knew?!) and I hate being pregnant. It was important to me to have at least two, though. Not only did we want more than one child, but I wanted them to have a sibling. I knew that came with responsibility, so believe me when I say there are things parents raising loving siblings never do.
Now, I don't think having multiple children just because you want someone to have a sibling is the way to go. You shouldn't feel pressured to have to provide your child with a companion. I know lots of only children and they don't lack for companionship or fulfilled lives. Most have never expressed even the slightest bit of sadness over not having siblings, either. Besides, there's absolutely no guarantee, in spite of your best efforts and intentions, that your kids are going to be close, or grow up to be buddies. It happens and it's no one's fault! And I don't think there's any tremendous shame in socially incompatible siblings not being close as adults. In my opinion, it doesn't mean you hate each other or anything, it just means "we're adults with our own lives."
That said, I think it's really beautiful to see adult siblings have a close relationship, and I would love that for my children. As such, I'm working on fostering companionship and closeness now, in hopes that it will flourish over time. To that end, I try my hardest to avoid all of the following: