Power of Attorney

IS it possible to assign power of attorney to more than one person: one for tax matters and another for all personal matters including personal finances if the principal becomes incapacitated or dies?

My husband appointed myself and his sister as power of attorney while he was deployed overseas for 10 months. His eldest son is 15 (from a previous marriage) and lives with my husband's parents. I was told that my sister in law was given power of attorney because she takes care of his finances (the 15 year old). Problem is, she has now started to use it to sign things using my husbands name with her POA about my son who is 9 months old. My husband is total supporting his sister, i am assuming because he doesnt want to rock the boat with her because she takes care of his eldest son's affairs. I have told him how i feel and he says i am being rediculous and he doesnt care what his sister does and can sign whatever she wants. I have a huge problem with this. How do i put an end to this and can she legally do this? I dont need her signing things for my son! she doesnt even see him. what can i do?

Is the person giving the Indiana Health Care Directive Power document allowed to give a directive document to more than one person or is the person restricted by law to just one person?

For an Indiana health care directive power document, is there a requirement that one includes the social security number of the appointing person on the health care directive document?

Can the health care power of attorney be valid with just one witness (non notary) in Indiana?