you can use server side and client side:
server side: disabled all validation in load function and enabled it when check the checkbox control and validate it by button click
client side : same but using javascript
HTML:
<asp:textbox id="txtName" runat="server" xmlns:asp="#unknown" />
<asp:requiredfieldvalidator id="RequiredFieldValidator4" runat="server" controltovalidate="txtName" display="None" errormessage="Please enter name">
ValidationGroup="info"
<asp:checkbox id="chkMarried" runat="server" onchange="enableddisabled(this);" />
<asp:button id="btnSubmit" runat="server" validationgroup="info"/>
and use ValidatorEnabled function to enable and disable the validation control in javascript
ValidatorEnabled(validationcontrolname,boolean);