If you're a fan of her fundie family, then you're probably already aware that Jana might be the most obsessed-over of all the Duggars.
Fans can't get enough of her, and for obvious reasons.
She's smart, she's beautiful, she's talented, and Jana is the only Duggar who might accurately be described as mysterious.
Don't get us wrong -- the Duggars all have their secrets.
But there's a difference between presenting a BS version of yourself to the public and being genuinely mysterious.
Most Duggars lack the depth for the latter.
After all, it's hard to cultivate a truly unique personality or any complexity of character when most of your waking hours are devoted to following rules.
Jana is probably just as committed as her siblings to the lifelong task of serving her God and her parents.
But in certain important ways, she's chosen to openly violate the rules as they were laid out for her.
Like her sisters, Jana was raised to believe that procreation is a woman's primary reason for being.
Unlike her sisters, however, Jana seems not to have taken that message to heart.
At 30, Jana is still single -- and, of course, childless.
That wouldn't be such an obvious follow-up statement in most cases, but the the Duggar ban on premarital sex is so strict that Jana would no longer be permitted to live with her parents if she had a child out of wedlock.
But live with her parents she does, which brings us to the next big mystery:
What is it that Jana does all day?
This question has often been phrased as "what does Jana do for a living?" but it's important to remember that as a Duggar woman, she's strongly discouraged from working outside the home.
(Certain jobs are deemed acceptable for females - Jill Duggar worked as a midwife for a time - but the idea of a woman making her own money is anathema to Jim Bob.)
As a result, Jana doesn't have a job in the traditional sense, but her days are filled with hard work, nonetheless. That's putting it mildly.
Try telling her the following isn't a full-time occupation:
Michelle Duggar made being a mom to 19 manageable by incorporating a "buddy system," wherein each older kid was assigned a younger kid to look after.
As the older siblings left the house, and Jana demonstrated a knack for nurturing children, the system gradually evolved to the point that Jana is now the primary caretaker to her four youngest sisters.
(In addition to Jana, there are nine Duggar kids still living at home, but five of them are 16 or older and probably don't require much in the way of supervision.)
Some say Jana's household responsibilities prevented her from starting a family of her own, as she never had time to find the right man.
Others say Jana longs to be married, yet chose not to leave the nest so that she could devote all her time and energy to her siblings.
Whatever the case, the upshot is the same. Jana is a full-time caretaker who shares a bedroom with four young women aged 10-14.
It's not a life that most 30-year-olds would choose for themselves, but it seems to work for her.
Of course, it's probably a little less pleasant these days, now that Jana is entirely on her own.
There was a time when Jana's friend Laura DeMasie occupied a very special place in her life.
Not only were they best friends, Laura actually shared a room with her and assisted with Jana's household duties.
A former Duggar employee tells The Hollywood Gossip that Jim Bob came to fear that Jana was in love with Laura.
And so, he had DeMasie sent away.
You didn't misread that. Jim Bob allegedly arranged for her to receive a job offer in Atlanta that she just couldn't refuse.
Maybe he was acting out of homophobia.
Or maybe Jim Bob just felt that Laura interfered with Jana's duties. Or a little of column A, and a little of column B.
We may never know. Bit whatever the case, the situation reminds of one of the most uncomfortable facts about Jim Bob:
He'd rather have obedient children than happy ones.