Can my name be added to a deed without both signatures of the owners and just 1

If they own as joint tenants with right of survivorship both must sign. If they own as tenants in common he can add you to his 1/2 interest in the property only. Consult with a real estate attorney who can review the situation and advise you fully. Use the lawyer finder tool here on to locate one near you.

Without seeing the deed it is hard to answer your question. I presume that you father and sister are tenants in common - meaning that each own a full 1/2 interest in the property. Your father then could, by Quit Claim Deed, transfer his 1/2 interest to whom ever he pleased without the signature of your sister. You can create situations that make the title unmarketable. You need to speak with an attorney in your area to discuss your options.

No. You need all current owners on the deed to sign a new deed to add you as an owner.