Yes, Pós (also spelled Poos, Poós, etc.) is a Hungarian surname; it derives from a diminutive of Pál (Paul).
If the sisters were all born after civil registration began (Oct. 1, 1895), then their births/baptisms are not indexed, although some of the records are online as browsable images (
https://familysearch.org/search/collection/1452460).
Unfortunately, 1925 marriages in Gelse are on the same microfilm as privacy-protected records, so FamilySearch's all-or-nothing policy means that they're not online. I don't have even that much of an explanation for why Komárom's records aren't available -- all they've got under that name is some post-WWII deaths and marriages. It's much too large a city for the registration office to have been elsewhere, so it's possible the earlier registers were destroyed in the war(s).