5 years is a tiny age gap (I expected a gap of at least 10 years, when I opened the thread).
My brother was 6 years younger than me and 5 years younger than Dsis.
We were both hugely excited when DM was pregnant, as we'd have a 'male' for out playing. Unfortunately, Dbro never grew as fast as we expected. However, by the time Dbro was 5, it was easier, although we never really 'played' together, we did play some of the time.
When I hit my teens, it was harder as Dbro was still a 'baby' to us. But he did mature pretty quickly, having two sisters helped.
When he hit his teens we were much, much closer.
When Dbro died (3 years tomorrow), I can honestly say it devastated me, Ioved him like crazy and am typing this through tears.
You will get lots of comments on how to facilitate strengthening their bond, but let it grow organically. They will learn. Jealousy is to be expected. It sounds as if DS is the most jealous at the moment (which makes sense as when he was a baby he monopolised your time and attention). tell him off for breaking her things, but it's normal, even with smaller age gaps (Dsis and I fought like cat and dog and I was very, very jealous of her closeness with dad).
FWIW my DD1 has two older brothers, both 18 years older than her. Whilst they adore her and there is no jealousy, I'm sad she will never experience what my siblings and I experienced.