system
Given the following post, respond as if you're commenting on Reddit:
human
[BTTF] Why didn't Marty McFly's parents recognise him?
gpt
The guys up at temporal control reviewed this one and although there is some mild distortion of the original time line to be fixed, there's nothing really to get your shorts in a twist about. As for Lorraine or George connecting Martin to Calvin, it was found to be highly unlikely for several reasons.

Firstly, the contact between Martin and his parents occurred over a six day period. Keep in mind that Martin was not with his parents for the entire six day period. Most of the time he was with Emmett Lathrop Brown (Yes, that ELB!), who showed remarkable foresight in trying to keep the temporal contamination limited.

Second, all of the contact between teenage "Calvin" and his parents ended 12 years, 6 months, 29 days before Martin was born. As baby Martin likely bore little resemblance to his teenage self, they would be unlikely to make the connection at his birth. 

Furthermore, they would assume that Calvin had continued to age normally after he left Hill Valley in November of 1955 when he had been roughly similar in age to themselves. That means by the time Martin began to show similarities to Calvin they would assume that Calvin was in his mid to late forties, not their teenage son.   

Finally, due to the amount of time passed and the relative brevity of their contact together it was decided intervention was not needed in this case.