Show Title
When first reading the title, one might think the show is about a house that is even more crowded than the 9 people who lived in the Tanner household by the end of Full House. But in fact, the title of the show seems to refer to the surname of D.J.'s belated husband, Tommy Fuller.
About D.J.
By the end of Full House, it looked like she got back together with Steve, but if that really happened, it didn't last forever.

We also know what D.J. did after she finished high school by the end of season 8: she went to college to become a veterinarian.

D.J. has two sons (J.D. (12) and Max (7) and is pregnant with her third child.

About Stephanie
Stephanie is aspiring a music career.
About Kimmy
Kimmy has been married, but also got a divorce. She is now a single mom, raising a teenage daughter, Ramona.

Compared to Full House
The premise of both Full House and Fuller House is a single parent raising three children, with help from their best friend and a close family member.

They turned the premise of Full House around though, the sequel is about a widowed mother with three boys, where Full House was about a widower with three girls.