The Labour peer George Foulkes has written to the Lords and Commons clerks asking them to review the rule barring peers and MPs from asking questions about the royals
There is no rule barring MPs asking questions about the Royal Family, assuming he is referring to Erskine May.
The fact that the government hasn't yet decided it wants to do so doesn't mean there isn't a mechanism to do it. Erskine May simply says it must be done in a proper manner.
I quoted the relevant paragraph on a previous thread - here it is again:
'As indicated at para 20.10, unless the discussion is based upon a substantive motion, drawn in proper terms, reflections must not be cast in debate upon the conduct of the Sovereign, the heir to the throne, or other members of the royal family.1 The same principle applies to the Lord Chancellor,2 the Governor-General of an independent territory,3 and judges of the superior courts of the United Kingdom4 (including persons holding the position of a judge, such as circuit judges and their deputies, as well as recorders).'