Happy Mother's Day to the kindest mom. P.S. Your kindness annoyed me when I was a kid

I wanted to solve this mystery, so I called her. I asked her where her kindness came from.

And it turns out it's not really a mystery. Just as her kindness eventually kindled my kindness, she credits her mother — my grandmother — for her generous spirit.

Growing up my mother had eight siblings. (She says the family was a "basketball team with a reserve.") Sometimes the children would come home for lunch from school — that was the practice in Kenya — only to find out there was nothing to eat because our mother had given their lunch to people who were passing by. Maybe these strangers looked hungry and tired. They'd surely walked a long way. So the sweet potatoes that her mother had been preparing for her own children were gone by they time they arrived.

But after half a day at school, my mother and her siblings were hungry, too. She recalls that sometimes they'd cry out of frustration if there was nothing to eat. Other times, their mother would give them some money to go buy bananas for lunch. And when there wasn't any money, she'd ask them to pick sugarcane from a neighbor's farm for their meal.

When there was enough food to go around, my mother's mother would feed not only her kids but their friends.

Flash forward to the years when my mother was raising my siblings and me. I asked: Did you know that we resented your kindness?

She said she did not. She was following in her own mother's tradition, and that's what mattered. When she knew families from her church or community were hungry, she'd invite them to our home. "How can they go hungry or be troubled if I can be of help?" she said.

So yes, as a child I was not thrilled by my mother's generosity. But now I fully understand how it came to be – and I know how it influenced me.

I am forever grateful for the seeds of compassion and empathy that she planted in me, my siblings and the hundreds, if not thousands of people that she has touched with her kindness.

I did ask her if she would have changed her habits if she had known that her own children were resentful. She told me she would never have changed, that nothing would deter her from being kind to others: "I would do it again and again."

Esther Ngumbi, is an assistant professor of entomology and African American studies at the University of Illinois Urbana-Champaign.

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