So my experience is a bit different as I had teen mom with ~5-7 year gaps between each siblings. Personally gaps are real nice if you have a choice. Less competition. But I think the real answer is team activities that are not competitive. I played comp stomp with siblings regularly. Taught my brother to play rts at 3. We still play together 25 years later. My youngest sibling just wants to do their own thing and the older ones didn’t encourage playing together so she’s more of an outsider. I remember she complained about it when she was like 5 but I wasn’t around much then to force it. I told the others to step up but they never did. If they did I wonder of things would be better between all of us.