Mine is kind of sad.
A neighbour and "family friend" (female) died in my early twenties. My mother for much of my childhood had not been mentally well so was in and out of hospital a lot, (never had a father) and I remember baking cakes, going on walks, watching TV and doing fun things with this family friend and always felt safe with her. Occasionally, she would spend the night in my mum's bed, and we were told it was because it was too late for the bus home. She was always there in the mornings before we woke up, made us breakfast, took us to school. I loved her possibly more than my own mother. When I was about 9, I made 2 mother's Day cards in school, one for my mother and one for this family friend. My own mother hit the roof, was pissed off at me and I was made to feel bad for thinking that way and told "never think that again. She is not your mother". At about age 12, I was asked by people in school if my mam was a lesbian. I didn't even know what it meant, and I was scared to ask my mother because she was pretty emotionally volatile.
About 3 months after the family friends death when I was 21, my mother told me I was conceived via sperm donation, the family friend had been her long term partner (and was slightly older with adult kids) and that they had intended to raise me together. However when my mother was pregnant, she grew concerned that I would be bullied or ostracized in school and m mother (as a result of mental health problems) kept questioning her sexuality and had a difficult time admitting her own sexuality to the world. This woman WAS (none biological, but definitely still) my mother.
I really hated that on her death bed, with my bio mum present, I couldn't tell her "thanks for being my mum" - I feel stupid now when I read this back because clearly she was my mum, but I never got the chance to understand and appreciate that before she died. Beyond her death, my relationship with my bio mum became even more strained and she has now passed too and I've also found out things about her, such as she started a love affair via weekly letters with an inmate in a local prison.