2nd cousin and her father, my great uncle both had aml leukemia at 50 and 66. no other of the 22 members in 3 generations had it. hereditary?

Coincidence: Acute myelogenous leukemia is seldom a familial disease. I would not be at all concerned. The one known gene is ataxia-telangiectasia carrier state, and this is not worth checking since the risk is small and you aren't going to do anything different (plan life, avoid exposure, early surveillance) in any case. I'm glad you're taking a proactive appraoch & sorry you lost your relatives early.

AML: There is a hereditary risk for aml. Multiple cases of AML developing in a family at a rate higher than predicted by chance alone have been reported. The risk of developing AML is increased threefold in first-degree relatives of patients with aml, but whether this places your family at risk is impossible to determine by internet. You might want to consult with a hematologist.