In The Big Honey Hunt, Brother was called Small Bear. But after Sister arrived in The Berenstain Bears and the New Baby, Small Bear became Brother Bear.

http://amzn.to/bearsbaby
Another cub was added to the family in The Birds, the Bees, and the Berenstain Bears.

http://bit.ly/B_Birds

The story focuses on the experience of Mama’s pregnancy as seen by Sister Bear. The baby is born at the end of the book. But Papa and Mama, in their excitement, forget to tell Brother and Sister the new baby’s name or whether it’s a boy or a girl.

A contest at the end of the book invited readers to guess whether the baby was a boy or girl and to name the baby. The winner received a complete library of autographed First Time Books, Berenstain Bears home videos from Columbia TriStar and CD-ROM games from Sound Source Interactive.

The Berenstain Bears and Baby Makes Five begins with the results of the contest: “The Bear family, who lives in the big tree house down a sunny dirt road, has a new member: a baby girl named Honey. What fun! What excitement!”
And so, our dear little Honey was born into our Berenstain Bears family!