That's on purpose
I could add a son for him, but it is very much on purpose that he has a different dynasty.
The Brachamios family as the family was called in Greek held several high positions in the ERE (The Doux of Cyprus is an actual recorded person from the family), which Philaretos also originally did. The reason why i didn't turn him (Philaretos) into a Brachamios is because we know his Armenian name. Also the Brachamios last name seems to have been used solely by the part of the family that actually became Orthodox after a couple of decades and Greek after a several decades more. And Philaretos didn't seem to have been more Orthodox than when his Greek masters disappeared from the east, he reverted immediately to the Armenian Church (Which is also why he isn't Orthodox before the ERE is beaten back from the East. If he was, he would start converting provinces)