There will be few family trees that don't have some illegitimate births in them. The question is - Who's the daddy?
I will share my experiences of researching illegitimate births here and I don't claim to have all the answers.
Most of those researched have been in Scotland the 19th century. I am not sure if the same stigmas applied then as is the 20th century. I suspect not.
If a daughter of the family had a child out of wedlock, in most cases the child was accepted into the grandparents' family. Sometimes the mother would be in a different household earning her keep as a servant. Sometimes when she later married her child would become part of her new family and sometimes would stay on with the grandparents.
The child if a girl would be named after her maternal grandmother following traditional Scottish naming pattern. A son though may have been given the name of his natural father. So do consider this.
Often the father would be someone close by, a neighbour as in the case of James Neil below. I have also seen cases where the reputed father suddenly upped sticks and emigrated!
As for how the birth was recorded, that depended on whether the father acknowledged the child.
From 1855 onwards either the mother alone is named on the birth certificate or the father also is named and signed the certificate. Illegitimate was written in brackets below the child's name.
If the parents subsequently married the child, under Scots law, became legitimate.
Where the father did not acknowledge the child there may well have been a paternity case where the mother sued the reputed father for aliment. You may be able to locate court records. More excellent information on this from Maxwell ancestry.
Pre -1855 the OPR baptism records have various wordings for illegitimate - natural son/daughter, bastard son/daughter, conceived in adultery, conceived in fornication. Sometimes the father is named and the parish he is from.
The mother would be brought before the Kirk Session (elders of the church of Scotland for each parish church and the moral compass for the parish) and asked about the father. If she named him he would be required to attend the Kirk Session meeting and they would be asked to repent and pay a fee in atonement. Similarly, if a child was born less than 9 months after the wedding the parents would be called up and accused of prenuptial or ante-nuptial fornication. So Kirk Session records can be a great resource. They can be accessed at your local archives centre. They have also been digitised but are not available yet to view.
If the baptism/ birth record doesn't yield any clues, the subsequent marriage or death certificates of the child may yield further information - the father may be recorded as "reputed father".
On several occasions I have found the child in a census with a different surname to his mother. I think to start with the child was given his father's name possibly in the hope that the father may do the decent thing and marry her or simply because that was the father's name and so the child should have its father's surname. Often the name later reverted to the mother's name.
Here is a typical example of Euphemia McCulloch born about 1850 ( no record) to Ann McCulloch, named Euphemia after her grandmother and recorded in 1851 and 1861 as McLeod. When Ann married Adam Todd she took his name. Euphemia Mcleod/ McCulloch/ Todd
And another the birth of James Neil in 1861 where his father signed the birth certificate. His father lived at 104 Peesweep Row and his mother at 103! The father soon married another girl and emigrated to Australia. Being illegitimate did not hold James back as he became Lord Provost (the Scottish equivalent of Lord Mayor).
