In the UK, 'X' is commonly used at the end of a message to represent kisses. Similar to 'Xs and Os' (kisses and hugs) in North America, however 'X' can be and is often used by people of varying familiarity (platonic friendships, siblings, crushes, dating, married, etc.) Usually more Xs means more familiarity. Xs can be seen used between two people of the same sex without being regarded as homosexual.
1) Hey are you still coming to London for my fancy dress
2) Heard you were back in town sexy. Haven't had a good shag
in ages, so how bout it? xxxxxx
3) Can you pick up some curry
for dinner on your way home love? Cheers x