Asking my MIL for permission for my boy name.

So we have our girl name picked out already and were struggling with our boy name (we both want a girl). My fiance's brother happened to pass away a couple months ago. We were all very close .. And I absolutely loved his his middle name. So if we have a boy I want to ask his mom if I could use his middle name as my sons first name and his first name as my sons middle name. Do you think that she would be okay okay with that? I dont wanna give out the names so I'm gonna use an example.

Her sons name - Joshua Michael

My sons name- Michael joshua

Update: I was planning on having him ask as we are all together.