In all honesty, the names of Gedimids do not sound Slavic in my ears. Gedimids also happened to have N1c1(L550+ & L551+) haplogroup which are found in high frequency among Lithuanian (south-Baltic) population.  Not Finno-Ugric subclade!

But Gedimids were Ruthenian (Slavic) rulers, as much as Rurikids were Russian rulers regardless of ethnicity or language spoken by the rules. Similar circumstances existed in most nations of Europe, so we cannot consider our rulers based on ethnicity alone. Gedimids were rulers of our ancestors and it’s a historical fact.

Yea, neither do the names Rurik, Olga, Vitovt, Swarog, Jarilo. But does the name Petr, Natalia, Klavdia sound Slavic? Not at all! Original Slavic names were pagan and not every name was a typical one like “Radimir” or Svetoslav. If  you don't exclude Polabian Slavs.
The rulers in Russia spoke Russia which was called "the language of the monarch (государь)".
That's exactly how today's Lithuanians want to prove they rulers of the GDL were "Samogitian". There's no prove – only lame claims based on that they have Vilno.