do you have options to your question?
don't be afraid to ask. if you really want to know why they suddenly don't talk to you, ask. but be polite while asking. tell them how you feel. if you feel upset about them ghosting you, say so. people cannot read your mind, so you need to let them know if this bothers you. if they say it's personal family matters, don't get offended. they need space if it's personal.