When i build à deck whit 1 star vampire i put 4 or 5 copy of this one in...

My question is : if i want to play whit 2 "star" what should i do ? 4 of each ?

good question .... If I play a star vampire, most of the time I put 5 copies in it because it turns out to be necessary - )
if you gonna put them both 4 times in your crypt, i think you gonna have a bad crypt draw too often. Maybe a ratio of 5 / 3 and and alternative for the last vampire if there is ... You can add anarch convert or tupdog in crypt to cycle it or might put some cards in your deck like effective management, recruitment, info highway, wider view ... or clan/skill specific cards: summon the serpent, soul scan, stranger among us, mesu bedshet, .... hope I mentioned something you didn't think of ...

i would say 4/4
but i still have nightmares about a game where a Kaymakli Nightmares in turn one moved all 8 copies to the bottom

it all depends on how effective your deck is with only one of those vampires

Noooooooooo Peter, the image of the kaymakli horror was just fading!! Lol!
Best advice ... just play weenie something - )

My "Marilutz" deck works pretty well with 4 Maris and 4 Lutz. Of course, there is the odd game when one of the two is missing and the deck is not optimal... but it still works with the "replacements" Rachel Brandywine and Quentin King.

In my Lutz Anarch Revolt deck I use 4 Lutz, 4 AC and 4 Lutz-backup or enhancers (Cybele, Aksinya, Nana, ...)
Not having Lutz in the opening crypt sucks, but having only Lutz in the opening crypt sucks even more.