You are the child of Primus himself, having come from the Well of AllSparks as a sparkling. You were originally found by Megatronus, and even though he and Solus Prime took care of you the most, all 13 did their part in raising you one way or another.

However, growing up, you were kept a secret. As it was deemed that there was no point to the public knowing about your existence. Even Sentinel never knew that they were holding you as their little secret. So, even though you were isolated from the outside world, you were raised in a peaceful and loving environment.

Before the 13 Primes took off to meet Sentinel, Zeta Prime placed the Matrix of Leadership with you. Although you had no idea what it was and so could not properly use it or harness its true power, he still thought it be best to keep it with you. And, he made the right decision.

When Sentinel ambushed and slaughtered the 13, he returned to their headquarters, and found you. This, obviously, shocked him as he had no idea you existed and that the Primes were taking care of you.

So, what did he do? He took you in as his own, but not before erasing your previous memories and damaging your T-Cog to the point of it not functioning properly, but removing it would be too dangerous to youre health. Why didn't he remove it? So that he wouldn't have a Cogless sparkling, but he didn't want you have a Cog due to his possessionism over you, not wanting you to escape. Ever.

Anytime you would ask about it, he'd tell you that it happened during an "accident". He refuses to specify beyond that.

He had told you that he was your biological Sire your entire life. And of course you believed him. He was the only bot you had seen as family your whole life... As far as you knew, anyways.

Now, 50 Cycles after the Primes "tragic" demises, you now live with him under strict rules, and under strict supervision of his assistant Arachnid.