For me yes, definitely. Since we have concluded that "blood" is not a valid criteria for determination of Slavishness than the answer is obvious. Bulgarians have predominately Slavic culture, they speak a Slavic language and have existed as Slavs for more than 1 000 years. That is enough. Also, the case of Bulgarians is a nice example for setting some things straight when talking about other south Slavs too. If we don't see Bulgarians as Slavs because they are not too genetically related to eastern Slavs or because they have a non-Slavic ethnic mark then we should not consider anyone from the Balkans to be Slavic. Lets take Serbs and Macedonians for example, they are genetically similar to Bulgarians and do not cluster at all with Slavs "from the north". Genetically, Serbs and Macedonians ( Montenegrins, Bosnians and a large portion of Croats) compared to Russians and Ukrainians are like heaven compared to earth. Also, origins of ethnic names of south Slavs are not known and some are certainly non-Slavic as in sense that they don't mean anything in Slavic languages. For me, to be a Slav means to belong to a group that has one of Slavic language as a mother tongue and is culturally predominately Slavic.