Named as the brother of Mordred in Renaut de Bâgé’s Le Bel Inconnu.
Segures may be identical to Sagremor (Sagramore), Mordred’s foster-brother in the Post-Vulgate Merlin continuation, or Seguarades (Segwarides).
Source
Le Bel Inconnu | Renaut de Bâgé, 1185–1190