the symbol of heart / hearts is used a lot .... e.g. by lovoo.com ...
so please don't use hearts
the core of the product / app / site is being alike somebody ...
he likes tattoos .. she likes tattoos
he dislikes tattoos ... she dislikes tattoos
he likes dogs ... she likes dogs
he hates school... she hates school as well
so maybe 2 faces / 2 heads / 2 people / 2 mixed twins ... could be a good symbol ? ...
but I dont want to cut your ideas / creativity
there is also a design mockup ... for the site .. it maybe helps
http://amtischladen.de (sorry about the strange url) .. and please ignore the old logo