You’re welcome M2AL.
My life was hugely enriched by having a sister and she’s wrapped up in all my happiest memories of my childhood. We can spend hours and hours reminiscing about our childhood together (and our teen years) and we usually end up crying with laughter. 
We were only 12 months apart so we did everything together, people always joke that we live in our own little sibling bubble even though we are late 30s now.
So yes, my childhood hugely influenced my decision to have a sibling.
However, my DH has a brother and they have no relationship at all. They grew apart as teenagers and now they don’t have any contact. They don’t dislike each other, they just have no desire to have each other in their lives.
Because he never saw the benefit to having a sibling he couldn’t understand why it meant so much to me to have a second child.
He did eventually come round but it took about a year of talking about it before he agreed to try for a second.
I have two sons now and they absolutely adore each other and my husband is so, so glad we had a second.
I really hope you get the outcome you want 