Me and my military husband got $600 on the rebate check and our single military friend got the same 600 back??

i am wondering why a single person and a married couple would get the same stimulus tax payment when i have a little more extra income. both my husband and his friend are in the military. do you think its because i didnt make much last year? i thought couples were suppose to get 1200 filing jointly...could someone help explai thanks alot