Gorm / Gommer

No reliable sources exist for this person. The ancestral line of Roger I of Montgomery is uncertain.

Gomeric, Prince of Denmark, built a castle in the southern part of the diocese of Lisieux known as Mons Gomerici. Mons means mountain so this would mean Mountain of Gormeric and hence the name became Montgomery at the time of his great-grandson.

Gomeric had three sons:

1. Bernard Danus, ancestor of the Dukes of Harcourt;
2. Sihtric, a Viking chief and the oldest son;
3. William (Guillam), Norman Baron.

from "Origin and History of the Montgomerys", B.G. de Montgomery 1948.

https://dcms.lds.org/delivery/DeliveryManagerServlet?dps_pid=IE1086074

NOTE from Alex Moes: de Montgomery claims that Gomeric was a son of Ingvar Ragnarsson and so a grandson of Ragnar Lothbrok, however, it is likely that he is confused with Ívarr Gudrødsson, King of Dublin. In either case the connection is unlikely as both Ivar's were active in the 860/870s making their likely births early in the 800s which is not compatible with de Montgomery's claim that Gomeric is the grandfather of Roger I, born 975.