well the people that say that are soooo wrong. it is 150% James but i guess they think that because snape loved her and in the beginning you can tell she liked him before she met james. go to
link and in the beginning of snapes memories as shown you will see his adventures with lily as children. you will see that in their first year at hogwarts lily and james met in gryffindor and eventually got married and snape and lily were separated when snape was put in slytherin. you will see that people must think this because of the love connection between lily and snape, anthough james is totally harry's father, not snape. Also, later in the memories, you will see that snape sends his patronus which is a doe (hmmm....) and dumbledore says "after all this time?" and snape replies, "always." hmm.... as you can see, lily, james, harry, and snape's patronuses are all types of deer. so when you hear this you aren't really sure what this is supposed to mean and you really don't get much help from the books either. Some people think that to have the same patronus as another person you must be blood-related somehow... which is possible but not really mentioned in the series, books or movies...anyway, i think some people might get the idea from this misleading conversation or idea. By the way, this scene is in DH (part 2) when snape dies and harry takes the tears to the pensieve and views snape's memories. Also, something interesting: snapes patronus is not a stag it is a doe, same as lily's. This makes me believe that if you love someone truly, your patronus is the same as theirs- it depends on what kind of situation. So because snape's patronus is Lily's, i guess people who believe the blood-related patronus thing must think that he is related to harry because harry is related to lily...Therefore, i think the reason why dumbledore says "after all this time?" is because he just figured out that because his patronus is a doe then he is in love wth lily. and snape probably says "always." because he is saying that he has always loved lily.