Great post EEE! The circumstances of my adoption were exactly as you surmised. My mother was 18, my father 19. He was Italian and she was not. His mother being a devout Catholic wouldn't permit them to marry and basically forced them to give me up. However, the relationship between my parents continued and so followed another pregnancy. "Nonna" must have decided that they couldn't keep giving babies away, or perhaps they were a bit older and more capable of making decisions for themselves? I am the eldest of 4 (all full siblings). My natural parents are still together.
Unlike others here, I have met up with my birth family. It has not been without drama - one sister is very religious (Seventh Day Adventist), the other suffers from bipolar disorder. My brother (13 years younger than me) seems relatively normal but is of a different generation to me. My natural parents are lovely people - very generous and kind - but we have little in common other than looks and DNA.
In my adoptive family, I was an only child, as were both my parents. I had only a few second cousins. In this new family, I seem to have hundreds of relatives - most of them first cousins - very overwhelming.
The whole adoption business is difficult. Birth parents wonder what happens to their offspring (my natural mother tells me how the death of her niece at age 3 made her start thinking "what if's" about me...). Adoptive parents (who generally become so due to an inability to have kids of their own) fear that their new child could be taken away from them at any time (I remember when I first corresponded with my birth family that my Dad cried when he saw their photos. He said "They all look so nice" as though he wanted not to like them). As for the adoptee, their new family might not be ideal (I was very fortunate) and there are often self doubts and identity crises. For the siblings in the birth family (who often don't know of the existence of the adoptee), there can be rivalry and jealousy (sister no.2 in my case...).
I was incredibly lucky. I was taken from a country town. My natural parents were orchardists and potato growers. They worked very hard, but didn't have a lot of time to devote to children. By contrast, my parents were city dwellers and I was the centre of their universe. I had every opportunity to do whatever I wanted to do.
However, before I met up with my natural family, I had to attend group counselling with other adoptees. Some of the stories that I heard were awfully sad - despair and maltreatment in their adoptive families and rejection from their birth mother. Like I said before, adoption isn't the quick fix to unwanted pregnancy that those who advocate it might wish.
