In reply to Have_A_Doubt:
It behaves as 2 separate variables, one for each sequence. Thus, it is equivalent to:
sequence s1;
int x1, x2;
( a ##1 b, x1 = data , $display("T:%0t For 1, x1 == %0d ",$time,x ) ) // seq1
and
( ( d ##1 e, x2 = data , $display("T:%0t For 2, x == %0d ",$time,x ) ) ##1 (data1 == (x2 + 1) ) ); // seq2
endsequence
ap4:assert property( @(posedge clk) s1);