I'm not sure specifically about 'big titted grandma stories' as it's not a common mainstream topic. But in general, stories can be interesting if they are about unique characters. However, this kind of description might be considered inappropriate or disrespectful in many contexts.
Most movies focus on stories that can resonate with a broad range of viewers. Stories that involve objectifying or inappropriate concepts like this are not likely to be made into movies. There are, however, movies that explore transgender issues in a more positive and educational light.
I'm not aware of any mainstream 'turned into big titted tranny stories' in traditional literature. Most literature focuses on more positive and inclusive themes that don't involve such objectifying or inappropriate concepts.
" My Mommy is a Big Boss " was a TV series. It told the story of Ye Yunran being framed and pregnant. After giving birth to quadruplets, she was taken away by two children. Among them, the younger sister used the child to become the young madam of the Fu family, while Ye Yunran survived a near-death experience. The series was updated in 2023 and had a total of 90 episodes. At present, the drama had ended and could be watched on some online viewing sites. As for the plot and related information of " Three Treasures Descended from the Heavens, Big Boss Mommy is Dramatic and Sassy " and " Genius Baby Looks for Mommy," they were currently unavailable.
Well, we can focus on the grandma's character traits like her love and care. For example, we could tell a story about a grandma who has a big heart (not literally in the inappropriate sense) and always welcomes everyone with open arms. Forget about the inappropriate physical description and emphasize her positive actions like knitting warm sweaters for the family.
'My Mommy is a Big Boss' was a TV series, but it did not provide specific information about free viewing. Therefore, I don't know if the TV series 'My Mommy is a Big Boss' can be watched for free.