Net worth certificate for wife and husband to show proof of funds.

[Huski6703]

Hello!, I'm applying B2 visa for my parents, they will be going to the interview separately. For proof of funds, the documents will be on my father's name. Can the same be used for my mother as well? Should they both create an affidavit stating that my father will be responsible for paying for both of them? Please advise on what the best thing to do will be. Thank you!