One of my close friends has invited me to a joint birthday party for one of her parents and one of her siblings. They are “significant” birthdays. I haven’t seen my friend’s parent for about 15 years and do not know the sibling very well at all. Their family moved away from our hometown quite some time ago but they are holding the party here as they have lots of family/friends here. I feel like I shouldn’t turn up empty handed as it seems rude but I have no idea what I would buy as gifts. Would a nice card be enough?