Re the Grundle/McQuillan marriage I added to my first post, I can now see, from a free Ancestry search, that someone has a tree there for the couple, with at least a few children named. None seem to match the siblings names you listed, so perhaps this marriage can be ruled out. Still, if you have an Ancestry subscription or start a free tral, you could contact the tree owner to see if they have come across any of the names you have, which are in a similar timscale.
Meant to add, if any of the siblings you listed are still alive, you will need to remove their names, as Rootschat has a 'no living person/s' policy.