This is so vague, but I'm hoping maybe someone knows what I'm talking about. It was made in the 1980's for sure, probably first half. There may have been more than one movie or special where they return. I know it was not animated or puppets. I think it was siblings trying to find something or someone in a fantasy world? I remember them going through secret passages or caves. It was definitely a fantasy live action. That's all I got for now. I'll add to this if I can remember more details. I used to love when it was on TV back in the day! I'm almost positive it was a TV only movie as that's the only time I ever saw it. Thanks!

I know I know! It's like all mumbled memories on the tip of my tongue. Maybe they stumbled upon this fantasy/secret world while running in the forest? It may have been some sort of mini series or TV special?