It would seem that you are correct in that using SKReceiptRefreshRequest to get a new receipt onto the device does not fix this issue since the new receipt still does not include the purchases by the other family sharing members.
However, calling SKPaymentQueue.restoreCompletedTransactions appears to generate a new receipt on the device that does now include purchases from other family members.
You don't need to actually process any of the restored transactions, because it is just a receipt we are after, you just need to call it to get that new receipt containing items purchased by other family members.
This is very hard to fully workout why this is happening as it is not possible to enable Family Sharing in the Sandbox environment and debug.
Harman78 can you confirm this is the behaviour you see as well ?
Can anyone from Apple shed any light on this ? It's not in the docs.