As commanded by lord Shri Rama , Shatrughna becomes the king of Mathura after killing Lavana. So now Shatrughna is the king of Mathura. I want to know that , is kansa from the family of Shatrughna as we know that he was ruling Mathura when lord Krishna took birth.
Kansa was from Chandravansha > Yadava > Bhoja family.
The wicked son, of ill-regulated soul, of the old Bhoja king, having usurped his father's sovereignty during the latter's life-time, subjected himself to death. Indeed, Kansa, the son of Ugrasena, abandoned by his relatives, was slain by me in a great encounter, from desire of benefiting my kinsmen. Ourselves with our kinsmen then, having paid due honours to Ugrasena, the son of Ahuka, installed that extender of Bhoja's kingdom on the throne. ~Mahabharata: Udyoga Parva
On other hand, Shatrughana was from Suryavansha > Ikshvanku > Raghu family.
So, Kansa was NOT from the family of Shatrughna.