Donovan brothers from Durris?

[Wexflyer]

Other children born to Michael and Jane
- Daniel, March 1875
- Bridget, Jan 1877
- Mary, Oct 1878

[Wexflyer]

Civil registration for Daniel in 1875. Father now a publican!
https://www.irishgenealogy.ie/files/civil/birth_returns/births_1875/03095/2134804.pdf

[Gortinanima]

Well, if Michael was 20 on the 1901 census and 30 on the 1911, then he was born ca. 1880, not 1882 as on the family tree.

So here is a good candidate.

Michael Donovan, son of Michael Donovan and Jane Donovan, bapt. Durrus 7/11/1880.
https://registers.nli.ie/registers/vtls000634871?locale=en#page/134/mode/1up

I had considered this family but no son John Donovan  recorded in the civil registration records.

[Wexflyer]

Well, if Michael was 20 on the 1901 census and 30 on the 1911, then he was born ca. 1880, not 1882 as on the family tree.

So here is a good candidate.

Michael Donovan, son of Michael Donovan and Jane Donovan, bapt. Durrus 7/11/1880.
https://registers.nli.ie/registers/vtls000634871?locale=en#page/134/mode/1up

I had considered this family but no son John Donovan  recorded in the civil registration records.

Well, where is Michael's (the father's) death in the civil registration records?

How many Michael Donovans, son of Michael Donovan options do you have to pick and choose from, born in Durrus ca. 1880?

Hint - precisely one?

As for not finding John's birth, multiple possibilities.
- Never registered.
- Registered, but misindexed/mistranscribed.
- They had moved. No sign of any of family in the area in 1901 census.

[Wexflyer]

The civil marriage registration does say father is deceased but not where he was from.

I believe OP was referring to the parish register entry for the marriage

[Gortinanima]

Well, if Michael was 20 on the 1901 census and 30 on the 1911, then he was born ca. 1880, not 1882 as on the family tree.

So here is a good candidate.

Michael Donovan, son of Michael Donovan and Jane Donovan, bapt. Durrus 7/11/1880.
https://registers.nli.ie/registers/vtls000634871?locale=en#page/134/mode/1up

I had considered this family but no son John Donovan  recorded in the civil registration records.

Well, where is Michael's (the father's) death in the civil registration records?

How many Michael Donovans, son of Michael Donovan options do you have to pick and choose from, born in Durrus ca. 1880?

Hint - precisely one?

As for not finding John's birth, multiple possibilities.
- Never registered.
- Registered, but misindexed/mistranscribed.
- They had moved. No sign of any of family in the area in 1901 census.

All good points.
Thank-you for your input much appreciated.