Data source is the files of Stella M. Mumma.
Data soure is "Early Dauphin Co. Families and their Descendants"
The 1900 Census lists Stella as living at home and being born Feb 1882 and Gilbert as 1884. Mary is listed as giving birth to 3 children, 2 are still alive which would be Stella and Gilbert. There is a conflict between Gilbert's birth with the census and his tombstone.
Shoop's Church Cemetery - Dauphin County, Pennsylvania
http://www.interment.net/data/us/pa/dauphin/shoops.htm
MUMMA, Gilbert Henry, b. 18 Apr 1890, d. 11 May 1932, par. (Isaiah & Mary SHELLAHAMER MUMMA, [SH]
MUMMA, Isaiah, b. 3 Feb 1859, d. 14 Jan 1927, sp. Mary SHELLAHAMER, [SH]
MUMMA, Mary SHELLAHAMER, b. 6 Mar 1859, d. 27 Jan 1950, sp. Isaiah MUMMA, [SH]
MUMMA, Stella Mary MUMMA, d. 01 Nov 1974, par. (Isaiah & Mary SHELLAHAMER MUMMA, [SH]
Commemorative Biographical Encyclopedia of Dauphin County, PA 1896 by J. M. Runk & Co.
"Mumma, Isaiah, was born in Fishing Creek Valley, West Hanover township, Dauphin County, Pa., February 3 1859. He is a son of John and Sarah (Flory) Mumma, a sketch of whom appears elsewhere in this volume. In his boyhood he had opportunity for securing an education in the public schools. But he was a very industrious helper in farm work, and in haste to be engaged in the actual business of life. He tried farm work until he was twenty years old, and then concluded it would be better to learn a trade. Accordingly, in 1880, he went to learn the business of a carpenter and continued in it for three years. He afterwards resumed farming. He was married, April 18, 1880, to Miss Mary, daughter of Thomas and Kater (Raver) Shellahamer. They have and three children, two of whom are living: Stella M. and Gilbert. Mr. Mumma is now managing one of his father's farms. he is a promising young farmer and esteemed by all who know him."