Only Grown-up in the family (Request)

After the great shift had shifted 80% of the world's whole population, some were suffering and some were enjoying their new life. But Jim a 19 year old college going boy was just suffering. Jim had ended up into his 37 year old Mother named Heather. Heather was shifted into the body of a horny 13 year old teenager,who only had perverse thoughts on his mind 24/7. 

One time Heather was even caught peeking in on her(his) daughter Kelly who was 17 year old and was the only one in the family to remain unshifted.

Jonathan the head of the family and the father of three was found in the worse possible situation. He had been shifted into the biological daughter of his son's new body that is he had been shifted into the body his baby girl named Sandra.

He hated that he had it all worse.

Jim was helpless,he had to breastfeed Sandra. All and all now Jim was the only grown up in the family,he had the job to put food on the table for his family. Jim didn't even had any skill,he didn't even possess any of his mom's knowledge. But surely his mom's body was pretty much attractive for her age. Maybe he could put the body to some use.