There is no current way of adding a marriage between siblings; the closest that you can get is first cousins and step-siblings (who don't share any of the same parents). I hope your Mughal family tree goes well. Here are a few sites you can use:
This answer comes from the question of: "How do I create common parents for 3 siblings already in the tree?"
"Add parents to any one sibling, then for the other two, go to Change and Delete > Change Parents > Choose New Parents from Tree and select the parents names. Hope this helped!"
The result is that the info is in correctly but the display is not ideal.