The last of the line of the 'Macedonaian' dynasty were, as we know, the childless sisters Theodora and Zoe. In order to preserve stability Constantine Monomachos was wed to Zoe. Constantines partner, and according to some also his wife, Maria Skleraina was installed as having imperial status with titles like Despoina, Sebaste and Basilissa. Maria Skleraina was not just a 'maitress' as has been proposed by some. She was a part of the imperial family machine.
Among the main sources for byzantic history are of course Psellos, Skylizes and Attaleiatos and later Anna Komemna.
When using facts from Psellos it is vital to understand that he was himself also one of the most important political players in Constantinople (Alf Henriksson, Byzantinsk Historia, 1971). Psellos had had important functions under earlier emperors and was for a while exiled. It is true that Psellos was a very well educated person and his work is a well for knowledge of the history of Byzans.
But Psellos was also involved in the coming power-play for creating future rulers for Byzans as he had been involved in the circus with lovers/favourites rulers around Theodora and Zoe.
If there is missing information about offspring from Constantin it may very well be for political reasons. The byzantine elite would hardly encourage other parties interfering in politics after the death och Theodora, Zoe and Constantin.
So Psellos role was not just to record historical events for a chronicle. He was one of the players in the very intricate intrigues regarding the power in Constantinople.