Looks:

Designation: Tinslash
Age: n/a
Color: brown and grey with purple wings
Optics: purple
Affiliation: Autobot/insecticon
History: Tinslash was hatched in an odd situation. He belonged to a hive yes but he also belonged to an autobot family. Having an insecticon mother and an autobot father, he was constantly teased or bullied for what he was. Knowing he wasn't needed in society he attempted to run away but he met an autobot who wanted to befriend him. Sideswipe, he explained to Tinslash that an insecticon like him could be used in the police force. He joined a few months later and became partnered to Sideswipe after a vow of silence was signed by Sideswipe. They'd fight crime together but Tinslash would speak for Sideswipe. And it continued like this for a while until that vow of silence was broken. Soon enough Sideswipe grew distant from his partner. Leaving Tinslash alone again, Tinslash ran away looking for a different refuge. He ended up finding Sideswipe again when they both joined another Insecticon in bringing terror to those who wronged them.

How he came to be:
Simple. What if both terror twins had Insecticon partners? To me I always thought Sideswipe would be somewhat jealous of the attention Bob received from Sunstreaker and found himself mostly alone as his twin played with his pet. So, based off of an insecticon from TFP. Tinslash was born just for company.