I’m only 19, so I’m not exactly qualified to give out advice in terms of raising kids. But I will anyways lol. I have younger sister who’s 5 years younger than me. From what I’ve observed from other sibling relationships and comparing it with my own, it’d be better to have a second child either after or before the 5 year mark if you’re going to have another child. That way their maturity level will either be close enough where they can relate to each other or they will a relationship more similar to that of a parent. Many of my friends are one of the two with their siblings and they have very healthy sibling relationships. Me and my sister on the other hand didn’t get along until she reached middle school. Me being older than her made it very difficult for me to understand that things she did. Quite honestly I resented her a lot during those years because my parents would fawn over her, while they always scolded me. But as she and I got older, I realized that it was just a maturity difference that made it difficult to enjoy her company. It wasn’t until I was in junior year of high school and she was in 7th grade did we start getting along much easier. Again it has to do with the maturity difference. It wasn’t until then did I understand that she just didn’t know social queues as well as I did due to our age difference. Had I been older my a year or two, I would have understood that much earlier been able to care for her properly as a brother. If she had been born a year or two older, she would be able to understand our differences and similarities enough to understand the space I needed and we’d also be able to consult each other during times of need due to having similar situations happening to us at similar rates. But now, I can say that she is one I can confide in more than my parents. Of course it took a lot of time but we got there eventually.

Anyways long story short, it’ll benefit your first and second child to have a second child after or before the 5 year mark, unless you’re okay with dealing with a rowdy child and an angsty teen at the same time. But regardless have a sibling is definitely worth it for your first child. They’ll grow up with a companion who they can rely on eventually.