Children's book legend Jan Berenstain -- who co-created the Berenstain Bears -- died Friday at 88-years-old after suffering a stroke ... this according to her family.

Jan and her husband Stan Berenstain created the Bear family -- Mama Bear, Papa Bear, Brother Bear and Sister Bear -- back in 1962 ... when they published their first book, "The Big Honey Hunt."

Since then, they fired out more than 300 stories.

According to Jan's son, Jan suffered a severe stroke on Thursday and died the following day.

Stan died back in 2005 at the age of 82.