You are required to disclose your marital status when you apply for a mortgage. We provide an overview of a mortgage application (form 1003) as well as an example mortgage application on FREEandCLEAR for you to review. Please see the "III Borrower Information" box on the bottom half of the first page of the loan application document where the borrower is required to select their marital status.
The good news is that you are required to complete a separate mortgage application than your parents and you can ask the lender to not disclose your marital status or provide your loan application to your parents. Please note that loan applications for all borrowers may be included in final mortgage documents that borrowers receive when the mortgage closes so your parents may be able to review your loan application. You may be able to ask your lender to not include your application in the final documents but the decision on what to include in the closing package is ultimately up to the lender.
Please also note that your marital status may be disclosed on the title documents (the documents that outline the ownership of the property) so that is another issue to keep in mind. I recommend that you have a confidential conversation with your lender and potentially the title company to understand the best way to handle the situation.