You already have a certain amount of information - your own and that available on sites/sources provided on this thread.
You have listed the family as (I'll put them in alphabetical order):
*Anita
*Dennis
From the NAA site, you have Denis Woodleigh CROSS, b 8 April 1925 in Canberra, enlisted in Bathurst NSW; next of kin John CROSS
*Molly
*Patricia
*Rosemary
From the NAA site, you have Rosemary CROSS (so she was presumably unmarried at that time) as the next of kin of John Thomas CROSS (presumably her father)
*Leanora Kathleen
You say she was b ca 1921, married 1944 in Seymour Vic, and died 1988. Do you have her death certificate? If not, you really need to get either her marriage or death cert in order to find out when and where she was born, etc, etc
*Terry
From the NAA site, you have Terence John CROSS, b 10 Dec 1818 in Queanbeyan (Queanbeyan is in NSW though adjacent to the ACT). Terence's residential address when he enlisted in Canberra in 1937 was Durville Cres, Griffith, ACT - which was also the address of his next of kin, John Thomas CROSS
From the NAA site, you have John Thomas CROSS born 6 April 1887 in Balmain (I can't find such a birth on the NSW BDM site) who enlisted in Canberra citing Rosemary CROSS as his next of kin.
It really has reached a stage where you need to purchase some certificates.
Regards,
JAP