By no means conclusive but there is no obvious immediate familial link and no reference to such in his bio. David was born and raised 2,500 miles from the stomping ground of Californians Dack & Dirk.
Dirk was in "The Virginian" for one ep. but Dack appeared in "Gunsmoke" and "The Guns of Will Sonnett".
If you wish to delve further into the Rambo lineage, Dack & Dirk can be found in RAMBO59.TXT (XXXXG21282 & 3) of RamboBook, although date of death for Dack is missing and that for Dirk is incorrect! Perhaps David exists within the annals also.