I have no other information on this family at this time.  The records for families of this age are based on the writing of Snorri or Adam Bede which may be more mythical than historical.  Firm birth and death dates are unreliable. 

The Foundation for Medieval Genealogy states:

 Adam of Bremen records that "Hardegon filius Suein" deprived "Sigerich" of the kingdom, but qualifies this by saying that it was uncertain how many kings reigned in Denmark during this period.  The passage is undated but immediately precedes the recording of an event in 915.  The Chronicon Roskildense records that "[Swen] huius filii Gorm et Hartha Knut" invaded Denmark, killed "rege Danorum Haldano cum filiis eius" and divided the kingdom between them.  This passage in the Chronicon Roskildense is confused but appears to refer to the same Hardeknud as Adam of Bremen, but making him the brother instead of father of Gorm. 

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Adam of Bremen records that "Hardecnudth Wrm…crudelissimus" was ruler in Denmark, and that "Worm regem" was forced to sue for peace by Heinrich I King of Germany who captured "apud Sliaswich, quæ nunc Heidiba dicitur".  It is unclear from these passages whether both deal with the same individual "Hardeknud Gorm" or with two separate individuals "Hardeknud" and [his son] "Gorm".  Snorre names Gorm as father of Harald King of Denmark, and "King Hordaknut" as the latter's grandfather   [FMG - Danish Kings]