I'd suggest solution utilising single RichTextBox
:
<RichTextBox IsReadOnly="True" IsDocumentEnabled="True" >
<FlowDocument>
<Paragraph>
Please enter your details for login: questions follow the link
<Hyperlink NavigateUri="https:" RequestNavigate="Hyperlink_RequestNavigate">Reset Password</Hyperlink>
</Paragraph>
</FlowDocument>
</RichTextBox>