I need to get Document signature by Spouse and its

On a contract i am currently having digital document signature by the signer. But there is a business need in which we need to get the signatures of spouse (in case there is a spouse). and we don't know currently if there's a spouse or not in our application(we don't have data about spouse so it can't be done within our application). So what needs to be done is - Our main signer will sign first and if there's a spouse that can sign then he will give the PC to spouse and spouse will sign too (the document will be sent to the same email address).In case there is no spouse then spouse signature will be left blank and document will be completed without it.

The scenario that you want to achieve is entirely possible, but your application must determine whether or not there is a second signer (spouse), and provide that information to DocuSign at the time of Envelope creation (i.e., must create the envelope with 2 signers if there is a spouse that needs to sign). Additionally, if you want the first signer to simply pass control of the computer to the second signer when it's their turn to sign (i.e., you're using embedded/captive signing for both recipients), your application will have to broker this interaction as well.

For example, the flow/logic would look something like this (for the two-signer scenario):

Your application collects information from the user to determine that there are two recipients/signers (current user = first signer, spouse = second signer), and collects the name and email address to use for each signer (email address can be the same, but name will be unique for each signer).
Your application sends a Create Envelope API request to DocuSign, specifying that there are 2 signers, both signing as embedded/captive signers (i.e., set the clientUserId property for each recipient in the API request).
The signing session for the application user (i.e., first signer) is initiated from within your application -- i.e., your application sends a POST Recipient View API request to DocuSign and uses the URL from the API response to launch the signing session for the first signer.
When the first signer submits his completed envelope, DocuSign will redirect him back to the page within your application that was specified as the returnUrl in the prior POST Recipient View request. The logic in this page of your application would identify that there is a second signer for the Envelope, and would present a message like "Please pass control to [spouse_name]. [spouse_name], please click the button/link below when you're ready to sign."
When the button/link is clicked (indicating that the second signer is ready to sign), your application sends a POST Recipient View API request to DocuSign and uses the URL from the API response to launch the signing session for the second signer (spouse).
When the second signer (spouse) submits her completed envelope, DocuSign will redirect her back to the page within your application that was specified as the returnUrl in the prior POST Recipient View request. The logic in this page of your application would identify that the Envelope is now complete, and display a message like "Your transaction is now complete. Thank you for signing..."

Please note that the above steps are a high-level description of the logic/flow for the type of scenario you described in your question. Actual implementation details may vary according to your specific requirements.