Having spent their first fifteen years in an abusive home in Michigan, twins Jacob and Jenee discover that they were born in a different dimension. As they reunite with their birth family and rediscover their birthplace Pontint. Jacob and Jennee learn that they are the future of Pontint, and had been hidden away to protect them from the royal family who wants them killed.

I like Richiev's format, but your plot interests me more. I can imagine it playing across the feature length. I'd suggest you go for a singular protagonist. Below is one way to pan it out across the blake synder narrative beat paradigm:
Setup: An abusive childhood on earth.
Inciting Incident: Discovering she's from an alternate dimension.
Break Into Two: The reunion with her people; discovering her birthplace.
1st half of Act 2: The political situation of their planet; what can she do about it? Is she different from the rest? which can lead us to..
Midpoint: She was hidden away in another dimension to protect her from the royal family who wants her killed; discovering her birthright??
2nd half of Act 2: The Royal Family closes in, and so on...

What's more? You can still have a twin (which is interesting) and define the lead character. Suggested Inciting Incident:? "After his twin from an alternate dimension pays him a visit..."

While this logline still has problems, I get a better sense of what the story is about.

The main problem this time is that your logline is all set-up and no forward story.
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"When they discover they're heirs to an otherworldly kingdom, a brother and sister must..." (Then tell us what they must do)