Question: 

My younger sibling has trouble holding a job and frequently asks for money from my elderly father.  A new car, a vacation, a house payment, you name it! He asks Dad for the money, and Dad continues to offer it up.  Not only does this decrease the potential inheritance for all siblings, it leaves less for our father's future care needs.

Answer: 

What is going on here?

 
You are describing a situation that we hear about far more often than one would think.  You have described entitlement.  Your brother has discovered that your father is a source of money, and he finds it easier to use your father to attain his desires.  I say desires because a new car or vacation is not a necessary expense. 
 
Unless your brother is disabled and incapable of working, your father may be fostering a dependent.  This has likely gone on for far too long. For some reason, Dad has willingly become part of this equation, and it would be good to know why.  Some parents cannot say no, even to their own detriment or that of their other children. 
 
Your father can do what he wishes with his money, but severely depleting his assets (at the risk of running out of money) is foolish, to say the least. We at Horizon see the elderly giving money to relatives when it is clear that they are not "set for life," themselves.  I often wonder if they believe those individuals will care for them later.  They may provide care, but there are never any guarantees.
 

What to Do 

You should understand that both your father and your brother may be quite defensive if you bring it up.  You will likely create a family rift by saying anything about your brother.  Yes, your brother is freeloading, and your father is a willing (or somewhat-willing) participant.  Unless you know for sure your brother is threatening your father, or your father is incapable of managing his own finances properly, it is NOT for you to challenge.
 
Talk to your father about his plans and resources for future care needs.  You may want to see if Dad will allow you to help him separate his assets into more manageable categories, i.e., those that he may need later and those he can gift without worry.  If you have been the responsible one, it is possible that your father will trust you.
 
If you believe that Dad is giving away money, you may decide that the potential rift is necessary.  Approach gently and kindly with your father, and hope for the best outcome.