Wedding Gift Etiquette

Hi Ladies,
Hope you can help with my situation. My cousin is getting married on Friday and my dilemma is this...my gift $$ from him was not very much (at least what I wouldn't have given if he married first) and I just thought it 'customary' to give what he gave to me, but now I am feeling kind of bad and I don't know if it should bother me this much. Do you or would you usually give what you get, even if it's family?
Thanks!