Darren’s death turns what was meant to be a vacation into a permanent move, leaving Nicholas to get to know 14-year-old Genevieve (Maeve Press) and 17-year-old Matilda (Kayla Cromer), who are the closest of strangers to him. “Let’s be honest: Am I the best catch?” he asks them matter-of-factly. “No, I am not.”

Like Freeform’s new “Party of Five” reboot, in which a family of kids raise one another after their parents’ deportation, “Everything’s Gonna Be Okay” is a variation on the teen-screen tradition of the Orphan Emancipation Fantasy. (The girls’ mother died years ago; Nicholas’s mom is still living in Australia.)

But where its channelmate deals with a socially and financially precarious family, “Gonna” sets its kids up comfortably. Darren, a lawyer, left behind ample funds and legal arrangements. Nicholas is an entomologist — each episode is fancifully titled for an insect species — but does not appear to work (though he keeps an impressive menagerie of creepy-crawlies).

Instead, the challenges are emotional and social. Genevieve is entering the embarrassments and cruelties of puberty, while Matilda is autistic — she’s high-functioning, but her trouble reading social cues levels up the difficulty of suddenly becoming the not-quite-a-father to a girl on the brink of adulthood.

A show like this lives or dies on this believability of its young actors, and “Gonna” has some of the best child casting this side of FX’s “Better Things.” Press’s Genevieve has a sensitive heart encased in an armor of spiky sarcasm. Cromer (who is herself on the spectrum) is a light bulb of an actress, instantly winning in scenes like Matilda’s eulogy for her father: “Dad used to get frustrated when I always made things about myself. But he is dead now. Surprise!”