Students loans that are in forbearance are still included when you apply for a mortgage even if you are not currently making a monthly payment on the loan. For student loans in forbearance, the monthly debt payment for the loan is calculated as either 0.5% to 1% of the outstanding loan balance or the full payment amount according to loan documents. So depending on the calculation method used by the lender, your full loan payment or 0.5% to 1% of your loan balance would be counted as debt when you apply for a mortgage, even if your student loan is currently in forbearance.
In the case of co-signing for a car loan, that debt typically appears on your credit report because you are legally responsible for the loan. If the car loan debt appears on your credit report then the monthly car loan payments are included in your monthly debt payments when the lender calculates your debt-to-income ratio for a mortgage.
I also recommend that you review your credit report to determine how these two loans are classified. You can access your credit report for free on websites like CreditKarma.com, Credit.com or AnnualCreditReport.com. We also provide a detailed explanation of your credit score and the mortgage process on FREEandCLEAR.