Difficult to say. Мама, папа, батя, бабушка, дедушка, баба, деда, тётя, дядя, and their dimunitives -- very likely yes. Strangely enough, "сестра" will hardly have such a vocative, I do not know why. On the other hand, "сестрица" might. So there are some irregularities. The whole feature being somewhat "optional" and "sub-standard", it's not surprising.Originally Posted by joysof