According to ancient curse, Silent Striders can't reach their Garou ancestors. At the same time, they tend to be haunted by wraiths from dark umbra - does it mean that such werewolf could have contact with his human parents/grandparents? And if so, would he be actually able to find them?
The Silent Striders can access the Dark Umbra (known as the Underworld by its inhabitants) where ghosts reside (the deep Umbra is something different). The rules had never been clear on how, although several books mention it. But in W20 core manual they finally included a level three rite to enter that spiritual kingdom (page 213).
So, yes, a Silent Strider could contact his dead parents and grandpas, but ONLY if these are wraiths (ghosts). Not every people become a wraith when the die, only those who had very strong ties to the world, unfinished business or strong passions, and could not transcend because they are not in peace.
Also, note that the Underworld is a very dangerous place, so even if your father died and became a ghost, he could have been destroyed easily (even by himself).
There are a few things that make this idea not work.
"Haunted by wraiths from the deep umbra" does not equate to a spirit contact background rating. For the distinction, look at the Medium merit, and the Haunted flaw (Text taken from the VTM versions of these merits and flaws, since its what I have on hand.)
MEDIUM (2-PT. MERIT) You possess the natural affinity to sense and hear spirits, ghosts, and shades. Though you cannot see them, you can sense them, speak to them and, through pleading or cajoling, draw them to your presence. You may call upon them for aid or advice, but there will always be a price.
HAUNTED (3-PT. FLAW) You are haunted by an angry and tormented spirit, most likely one of your first victims. This spirit actively attempts to hinder you, especially when feeding, and does its utmost to vent its anguish upon you and anyone in your presence. The Story- teller determines the exact nature of the spirit, its powers, and whether or not it can eventually be laid to rest.
The most important thing, however, is that the VAST majority of creatures do not become wraiths when they die. It is very unlikely that any particular living person today has a wraith ancestor.