The time tested ancient formula: take the older person age, divide by 2, add 7. That's the acceptable age gap to avoid major issues and scrutiny from society. Everytime I hear a story like this, I do the math.

22 ÷ 2 = 11
11 + 7 = 18

18 would be the minimum age for a 22 year old. Maximum age for a 16 year old would be 18.