Checking the birth records - brother Raymond was Ernest Raymond Foster - parents William Harrison Foster and mother Sarah E Owens.
Iva seems to be Mary Iva born 3 rd April 1907 - parents William H Foster and Sarah E Owens.
On a Michigan Passenger Crew List for 15th May 1923 - Port of Arrival :- Sault Sainte Marie, Michigan - Iva Foster aged 16 years, (which ties in with the information on the 1930 Census) exceot the birth date is given as 26th February 1907
Iva is a student. Accompanied by mother :- Sarah Foster and going to her brother Harry Foster, 81 S Terrace. Muskegon. Michigan.
Sarah Foster aged 42 years also crossed the border.
On the brief look so far, can't positively tie in a death record to Iva or Mary Iva - will have another look later.