i played a game i downloaded from this forum a while ago you play as a boy him and his sister have to go live with crazy grandpa who is a scientist or something he accidently sent your parents to another reality or something you walk around a town doing tasks for the grandpa you encounter nsfw scenes your trying to help get parents back you end up on some spaceship i think thats as far as my memory cant think lol hopefully someone knows what im talking about lol
Are you thinking of Monolith Bay? https://f95zone.to/threads/monolith-bay-v0-42-0-team-monolith.59278/ Very similar set up as what you've described. It's an uncle though and not a grandpa, so maybe not the one.
