Sure, the trick here is that contacts custom fields are served as a “platform” here, which is being re-used by the members custom fields.
All we need to do is to “connect” contacts custom fields with members, so members can update their custom fields data.
To connect fields, please go to “Contacts” > “Site Members” > “Customize Info”
Then click on “+ Add More Fields”
If you have any custom fields created on contacts - they will be displayed with the “+ Add” button near them. If there are no custom fields on contacts side - click on “+ Add Custom Field” and you’ll create a new custom fields
Let me know if I can help anyhow