A myth that haunts many only children is that we're selfish, whereas in actual fact we're just not so practised in thinking of others. The difference being that we're not mean, or unkind, just sometimes lacking the habit of considering the needs of others alongside ourselves. This can manifest itself in things like only children not offering a guest a drink, as we'd just presume you'd ask for one.
I read a book about only children once that explained that as we had little experience of our things being damaged by others (or food being eaten by others) we find unexpected changes in our possessions more challenging to cope with. If an only child leaves a chocolate bar in their room, it will always be there when we return. Things don't get changed unless we change them ourselves. The book explained that it isn't selfishness that makes us not want to share our chocolate bar, we'd just rather pay to buy a second one for you.
I digress. In my 30s, as a mature only child, I became self aware enough that sometimes my nature means that I don't always consider the feelings of others as much as I'd like to. I don't think I'm a mean person, nor did I mean to behave selfishly, but my tendency to just focus on my own little bubble meant I wasn't the person I'd like to be.
So this is an area I've been working on, and will continue to work on. To be kind. To be thoughtful. I'm not attempting to change my personality, just to enhance certain elements of it.
I also believe that what we seek, we should first find. If you want more love in your life, you need to become more loving. If you want better friendships you need to become more friendly. If you want more joy, you must first become more joyous.
I'm not perfect, nor will I ever be, but am I kinder than I was a few years ago? For sure. Will I continue to stretch and develop my thoughtful muscle? Hell to the yes.