I can be an art lover. a music lover or a lover of fine wine.
It doesn't necessarily mean I have sex with it.
I've never heard that it's a gay term before - the meaning can be broadly applied so although homosexuals/lesbians have lovers it's not exclusively used in that sort of context.
A dictionary is a useful thing to both adults and 9 yr olds but kids don't always think of looking up the meaning of words.
When our son asks me something I'm not sure of then I'll say "I don't know - let's look it up!".
Sometimes my guessed meaning is right but sometimes I learn something new.
http://dictionary.reference.com/browse/lover?s=t
lov·er
noun
1. a person who is in love with another.
2. a person who has a sexual or romantic relationship with another.
3. a person with whom one conducts an extramarital sexual affair.
4. a person who has a strong enjoyment or liking for something, as specified: a lover of music.
5. a person who loves, especially a person who has or shows a warm and general affectionate regard for others: a lover of mankind.