8th: OAG twigs

Ancestry's Recent Member Connect Activity alerted me to someone researching the family of David & Johnina (BAIN) OAG, so I had a look to see what light might be shed on exactly how many children Johnina actually had.
Time is running out for first hand knowledge as apparently there is only one of the children still living.
As yet I have no corroboration that Christina married to a James someone with children Alec, Dora and Jean, and supposed sister Janet married to a John someone with children Jean, John, James, do actually belong in this family.
Wonder if Janet is actually half sister Janet Flett BAIN instead? To date I've not sighted the latter beyond 1901.
Can anyone shed further light on this?