If you do what you're asking advice on how to get (ie a pic of your cousin's feet) - IMAGINE your 18th birthday when she's 16 and a judgmental teenage girl with a VERY juicy piece of dirt on you : all she has to do is let that slip to a girlfriend and, suddenly, you're avoided like the plague and have a reputation. Having a foot fetish is one thing (and mostly seen as being fine except by immature idiots), but having an attraction based upon your foot fetish, for your COUSIN'S feet is begging for people to treat you like dirt.
*Best advice is this* : never forget that, even in the unlikely event your cousin gives you what you want (ie pics of her feet), this will ABSOLUTELY come out sooner rather than later and potentially ruin you in your own family (it'll absolutely get out to your friends). SO, go to the yahoo search engine, turn off the adult filter, enure your computer has ANTI VIRUS protection (100% necessary), go to the 'images' section, type in 'foot fetish naked women' as a search string, and look at images of barefoot naked women.
Then, when you get to age 18, if you don't have a compliant girlfriend, go to a brothel and stress that you're interested in exploring a fetish.
WHATEVER YOU DO, do NOT tell anyone in your family about your fetish - don't tell your friends, don't mention it on Facebook, keep...it...to...yourself *except* if you get a prostitute (written literally as meaning rental porn, as opposed to my intending to insult you, which I'm not), or a girlfriend who isn't a close friend of yours.