Matthew Adam Simms is the first and only biological son of Adam and Eva Simms. Matthew is also the step-brother of Luke Simms (Adam Simms' first son with his first wife). Mathhew Simms was born around ten months into his parents marriage, in the season four episode called "A Most Precious Gift". He was born two months prior to the birth of Caroline Ingalls' fifth child, Grace Pearl Ingalls.
When Matthew's mother, Eva Beadle Simms, was about five months pregnant with Matthew, she spoke to Caroline Ingalls (who didn't know she was pregnant at the time), and expressed her feelings of anxiety and uncertainty about becoming a mother, for the first time, at such a late age. Eva explained to Caroline that she never even expected to be married, let alone to be a mother at such a late time in her life. Eva also explained that she didn't believe she could be a good mother and care for such a tiny and helpless baby, as she had never had siblings and had already set her life on track, being a single women and a school-teacher. How was she going to be a mother?
Caroline reminded Eva that out of all the mothers in Walnut Grove, she was the one who had most experience with children, and helping to bring them up, as she was the school-teacher of the village. "But," Eva explained, "They are five years old by the time they come to school...they're not necessarily needing diapers." After hearing this, Caroline told Eva that she had no need to be scared of being a mother and that once her baby was born, she would be fine and fall in love with her child, just like Caroline did when she had Mary. "Where did the time go?" cried Caroline, as she wished she could be a mother once again, not realizing that she was three months pregnant with her youngest daughter, Grace. After their discussion, Eva became more relaxed by the feeling of carrying her growing child inside her, and four months later when Matthew Adam was born, she fell in love with him, as did Matthew's father, Adam Simms. She even gave up her occupation as a school-teacher, to stay at home and nurture her newborn son, for the first few months of his life.