This can't be that far apart since Saul started his kingship early at 30
1 Samuel 18:1–4Be Successful
Too many Bible readers still view David and Jonathan as two frolicsome teenagers who liked each other because they had many common interests, but this picture is shallow and inaccurate. Jonathan had to be at least twenty years old to be in his father’s army, and the fact that Jonathan was already commanding one-third of that army and had won two great victories (13:1–4; 14:1ff) indicates that he was a seasoned soldier and not a callow adolescent. Some biblical chronologists
- I was referred to "the age difference between Jonathan and David could be 25 years"
- Something to consider is that Saul reigned for 40 years (as did David and Solomon). David came along toward the end of Saul's reign.