I remember that their grandmother had passed away, and the family, mom, son, and daughter, moved in. The father might have been there. The girl starts to notice that the house is not normal. Their mother grew up in the house and knew the people around. The girl starts to like one of the boys, but there is a male ghost that she soon finds out about and they start falling in love. The house is also haunted by a female and that is the male ghost's ex, who gets very jealous when she finds out about them and tries to kill her.
Possibly Ghost House, by Alexandra Adornetto?
Barnes & Noble description:
After the loss of her mother, Chloe Kennedy starts seeing the ghosts that haunted her as a young girl again. Spending time at her grandmother's country estate in the south of England is her chance to get away from her grief and the spirits that haunt her. Until she meets a mysterious stranger….
Alexander Reade is 157 years dead, with secrets darker than the lake surrounding Grange Hall and a lifelike presence that draws Chloe more strongly than any ghost before. But the bond between them awakens the vengeful spirit of Alexander's past love, Isobel. And she will stop at nothing to destroy anyone who threatens to take him from her.
Turned up on a Google search for
"ghost" "romance" -movie grandmother house. Most of the details seem to match, except that it's not (as far as I can tell) the whole family moving in to the house. (The Goodreads reviews seem to indicate it's a pretty awful book, though.)