The son of a sociopath

"He is not my son John." Sherlock said to him.
*****BOOM*****
"JACOB!" Both men ran into the apartment
"IM ALIVE!" the nineteen year old stumbled out of the kitchen with smoke covering his face. "So you were right about our experiment hehe." The boy rubbed the back of his neck.
"Why are you home?! You are supposed toe at school!" John opened the windows as Sherlock lectured.
"Yeah about that....I kinda got kicked out....."
"HOW?!?!"
"The professor was a dumbass!"
"I know that but we don't tell your professors that!" Sherlock pinched the bridge of his nose. "Go clean up we'll talk after dinner." Jacob walked to his room. "Not a word to Lestrade, John."

Or Sherlock finds a 5 year old boy when his mother was murdered. 14 years later Jacob Walters is 19 years old and Sherlock has taken care of him. They have solved many mysteries together but the one they never solved was who murdered Jacob's mother.