This is how it works. They hear you ask for a sign so they bring your awareness to something or someone that holds meaning to them and to you. They also come to you in dreams. These are real visitations. Remember, when your parents speak with you, they do so through thoughts.
Spirit communication is mind to mind.
Your parents are spirit now and their communication will be mind to mind. People seem to think all the thoughts they think are their own thoughts. Listen for your parents' thoughts. They want you to know they are ok. The Light is there for any spirit and all spirit.