I need to use a separate paper for my visa for siblings. Is there a format?

Lori, there is no fixed format for the invitation letter. Just remember that the letter should contain the following information:
a) Information on the applicant (full name, gender, date of birth, etc.)
b) Information on the visit ( purpose of visit, intended arrival date, place(s) of intended residence, intended duration of residence, arrival and departure dates, relations between the applicant and the inviting ndividual, financial source for expenditures)
c) Information on the inviting individual (name, contact telephone number, address, signature, etc.)