I've been on a bit of a parental Megatron kick for a while, so I'm just tossing a random idea your way. But anyways, a decepticon (probably Starscream) successfully kidnaps Bumblebee to present to Megatron. However, they were less than gentle, and bumblebee is badly injured. Megatron rewards this decepticon for their efforts by beating within an inch of their life. As it turns out, Bumblebee is Megatron's son. However, he kept it a secret for multiple reasons but all to protect Bumblebee (Bee knowing the truth is up in the air). Megatron then tries to patch up his sparkling, and when the autobots show up to rescue Bee, Megatron just so happens to let the autobots get away with Bee so that Bee can receive proper medical care because Megatron does not trust any decepticon medic with his son as far as he can throw them. Sorry if this turned out super long.