If you read a few of the comments, you'll find that breadman (the maker of the game) has answered this sort of question several times
When is the new update?: Breadman doesn't announce the update until about a week out, and that's only to the people who paid.
Please add more scenes with mother and sister: scenes/content with the mom is added every update. As for the sister, it's up to the voters to determine who gets more content. I believe it's a bit of the sister, but Brenda will be the main focus this coming update.
If you want to have a say in who is given more scenes, you'll have to pay