My bad, i should have explained why i chose the above answer. Sorry...
My reasoning is along the following line: (Assume pirates ranked 1-5 - descending seniority)
Consider only 3 pirates (i.e#1,2 dead somehow) :The best deal for the most senior, i.e, #3 is to give 1 coin to #5 and take 99 coins for himself. Certainly #4 will disagree since he is next in line (i.e he will have the chance to propose a division if #3 dies). But #5 will agree since if he disagrees to this deal, 2 out of three pirates against this proposal, and #3 will be killed. Next will be #4's turn and by then only 2 ppl left. #4's vote counts as half; #4 can choose to take all 100 coins for himself and #5 gets nothing.
Now consider 4 pirates(i.e just #1 dead): If the most senior now, #2, were to die, in the next level, that is when #3 is the most senior, #4 gets nothing, only #5 gets one coin and #3 takes 99 coins, as seen above. Now, there are 4 pirates, so for #2 to secure his proposal, he just have to get the vote of one more person. Hence, the best deal for him is to give 1 coin to #4 and takes 99 for himself; #4 certainly must agrees to this deal because if he disagrees, 3 out of 4 pirates against this proposal, #2 will be killed, it goes to the next step and #4 will then get nothing.
Now consider 5 pirates (as is our question): If #1 were to die, in the next step as described above, it turns out that #3 and #5 gets nothing - only #4 gets one coin and #2 gets 99 coins. So , if #1's proposal is not accepted by majority and he is killed, #3 and #5 gets nothing. So both of them will vote if they get at least something - so #1 just has to give #3 and #5 each one coin and take 98 coins for himself.
This solution is slightly different from the one i proposed above. In the above, I just added one more to the maximum #4 and #5 will get if #1 were to die. But i missed out this line of reasoning, which seem to give more for #1.
Of course, this is based on the fact that all of the pirates are both very greedy and very logical.
The hardest thing to understand is why we can understand anything at all -- Albert Einstein