Piranha on Family Tree Circles

My mother, born Joan Frances DYKE 7 February 1932, Montrose Hospital, Hobart. She died 26th September Blenheim New Zealand. Fathers particulars on her birth certificate not stated.
Mother stated as Alice Dorothy DYKE, born in England. She was 39 at time of Mum's birth.

*Adopted by W. & M.A. UREN as Joan Frances Miller record no A.O. 40/32.
**Re-Adopted by B.C. Miller as Joan Frances Miller record no A.O. 223/44. Adoption Cert dated 19/Dec/1944.

*William Salmon Uren was born 1864 in England. He was aged 68 at time of adoption!?? M.A.(Mary Anna Tonkin) Uren was born 1859 in England. She as aged 73 at time of adoption!!??? Assuming Mums' grandparents.

They had two sons living at time of adoption; William Harper Uren died January 1944. Leondard Sydney Uren born 1893 died ???? He was a dentist, moved to Penrith NSW. Cannot find his death.

William Harper Urens' last will and testament appoints his brother Leonard Sydney Uren executor of his will and he bequeathed all his estate both real and personal to Joan Frances UREN.

**B.C. Miller (Beatrice Clara Miller, formerly Reid nee UREN) born 1887 Bristol has to be Williams' sister, why did she adopt Mum?

So Mum's father never had legal quardianship of her, why??