1930 U.S. Federal Census; Montana; Pondera County; School District #10; Conrad; Roll: 1260; Page 4a; Enumeration District: 9, Image: 149.0; Enumerated on 11 Apr 1930:

ETIENNE, Michael J.; head of household; male; white; 64 years old; first married at age 33 years; born in Wisconsin; both parents born in Belgium; occupation: farmer--general farm.
ETIENNE, Elizabeth M.; wife; female; white; 49 years; first married at 21 years; born in North Dakota; both parents born in Canada; occupation: none listed.
ETIENNE, Thomas W.; son; male; white; 24 years old; single; born in North Dakota; father born in Belgium; mother born in North Dakota; occupation: laborer--general farm.
ETIENNE, Norman A.; son; male; white; 18 years old; single; born in North Dakota; father born in Belgium; mother born in North Dakota; occupation: none listed.
(NOTE: There seems to be a discrepancy between where Michael is listed as having been born--Wisconsin--and the sons listing Belgium as his birthplace. This could just be an error on the part of the enumerator. Errors are not uncommon in the census data).

1930 U.S. Federal Census; Texas; Bell County; Temple City; Precinct 5; Ward 3; Roll: 2291; Page: 15a; Enumeration District: 24; Image: 313.0; Enumerated on 14 Apr 1930:

ETIENNE, Leo M.; head of household; male; white; 28 years old; first married at 25 years of age; born in Montana; both parents born in U.S.; occupation: house painter.
ETIENNE, Grace H.; wife; female; white; 29 years old; first married at 26 years of age; born in Texas; both parents born in Texas; occupation: none listed.
ETIENNE, N. Jeanette; daughter; female; white; 1 year, 9 months of age; single; born in Texas; father born in Virginia; mother born in Texas.
HOLCOMB, Dorothy L.; stepdaughter; female; white; 11 years old; single; born in Texas; both parents born in Texas.
HOLCOMB, Josephine G.; stepdaughter; female; white; 9 years old; born in Texas; both parents born in Texas.
(NOTE: I don't know if Leo is related to the Montana Etienne family, but perhaps he is).
----------
MONTANA DEATH INDEX, 1907-2002 & SOCIAL SECURITY DEATH INDEX:

ETIENNE, Alfred H.
Born: 28 May 1907
Died: 20 Oct 1976 at age 69 years
County(s) of Death & Residence: Trout Creek, Sanders County, MT 59874
Marital Status: Married
Montana Index #: 5301
SS#: 389-18-6791

ETIENNE, Francis B.
Died: 22 Feb 1940 at 73 years of age
County of Death: Pondera County
Index #: 1322

ETIENNE, Louise M.
Born: 22 Jul 1904
Died: 22 Sep 1972 in Great Falls, Cascade County, MT
Marital Status: Widowed
Montana Index #: 4590
SS#: 268-28-4525

ETIENNE, Margaret
Born: 26 Oct 1906
Died: 23 Sep 1992 at 85 years of age
County of Death: Lincoln County
County of Residence: Trout Creek, Sanders County, MT
Marital Status: Widowed
Montana Index #: 4936
SS#: 388-36-2939

ETIENNE, Michael
Died: 25 Apr 1917 at 88 years of age
Montana Index #: 118-604
-----------
I hope you find the above information useful. If you go to your home page's "White Pages" telephone directory feature, you will find several "Etiennes" listed as living in Montana. They will give you the snail mail addresses and phone numbers. A phone call or two might be helpful to see if you can gather more information.

I am not related.