<A> has how many relatives?: Name the person whose mother name is <A> and has a son named <B>?
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_o: SELECT DISTINCT var_uri where  brack_open  var_uri dbo_parent <A> sep_dot var_uri dbo_child <B> sep_dot var_uri a dbo_Person  brack_close 