I understand that in England today, it is possible to create an entail based on age rather than sex -- that is, if the owner of the estate died without children, the estate would go to the oldest child of the next-oldest sibling, regardless of sex.

I know that during the Regency, the main reason for an entail was to keep the estate in the family, so entails based on age must have been very rare or non-existent, if they were legally possible. But were they legally possible?