I wouldn’t pathologize this attraction, but would rather see you continue to observe who you are drawn to, what the characteristics are of the men you fancy, and do you see other themes that develop other than age. Because you are drawn to people from a wide age range and you have elected to be in a relationship with someone of a similar age, it may have to do with a character trait or personality feature that transcends age.
Of course, the obvious element therapeutically would be to use a form of psychodynamic therapy to find out if there had been unmet needs by your father or older brothers that you may be trying to meet through the attraction. However, I’d take the first approach to understanding the theme represented by all those you are attracted to as that may be most helpful the soonest.
Wishing you patience and peace,
Proof Positive Blog @ PsychCentral